Light Jet - Legacy Production (Founding Variant of Beechjet/Hawker Line)
Mitsubishi MU-300 Diamond / Diamond IA: Complete Specs, Performance, and Buyer's Guide (2026)
Mitsubishi Heavy Industries
Mitsubishi MU-300 Diamond / Diamond IA: Complete Specs, Performance, and Buyer's Guide (2026)
The Mitsubishi MU-300 Diamond and its derivative Diamond IA represent one of the more unusual stories in business aviation: a Japanese-designed and built light business jet that became the founding airframe of what would eventually be the Beechjet 400/400A, Hawker 400, and Hawker 400XP product line. Mitsubishi Heavy Industries first flew the MU-300 Diamond on August 29, 1978, building 89 standard Diamonds between 1978 and 1985 plus 11 improved Diamond IA aircraft. In 1985, Mitsubishi sold the design rights to Beech Aircraft Company, who rebranded the Diamond IA aircraft as the Beechjet 400 and went on to develop the platform through 30+ years of evolution. Pre-owned market today (rare originals): $250,000 to $500,000.
For aviation collectors and operators willing to take on a rare Japanese-built light jet, the MU-300 Diamond represents an unusual and historically significant aircraft.
MU-300 Diamond / Diamond IA Specifications at a Glance
| Specification | Value |
|---|---|
| Category | Light Jet - Legacy Production (founding airframe of Beechjet/Hawker line) |
| Production Status | Discontinued 1985 (rights sold to Beechcraft) |
| First Flight | August 29, 1978 |
| Mitsubishi Production Period | 1978 to 1985 |
| MU-300 Diamond Built | 89 |
| Diamond IA Built | 11 (improved Part 25 certified variant) |
| Total Mitsubishi Production | 100 aircraft |
| Crew | 2 pilots |
| Passengers (Standard) | 7 to 8 |
| Passengers (Max) | 9 |
| Max Range | ~1,360 nm |
| Max Cruise Speed | 449 ktas |
| Long-Range Cruise | 410 ktas |
| Max Operating Altitude | 41,000 ft |
| Engines (Original Diamond) | 2× Pratt & Whitney Canada JT15D-4 |
| Engines (Diamond IA) | 2× P&WC JT15D-4D (improved Part 25 compliance) |
| Thrust per Engine | 2,500 lbf (5,000 lbf total) |
| Cabin Length | 15 ft 6 in |
| Cabin Width | 4.92 ft (59 in) |
| Cabin Height | 4.75 ft (57 in) |
| Pre-Owned Price (2025) | $250,000 to $500,000 |
History as a Japanese-Built American Light Jet
The MU-300 Diamond was Mitsubishi Heavy Industries' first business jet, designed and built in Japan but specifically targeting the U.S. market. The aircraft was named "Diamond" rather than receiving a numeric designation typical of Mitsubishi's product line.
Platform timeline:
- 1978: MU-300 Diamond announced
- August 29, 1978: First flight
- 1978 to 1984: Production of standard Diamond (89 aircraft)
- 1984: Improved Diamond IA introduced (Part 25 takeoff requirements)
- 1984 to 1985: Diamond IA production (11 aircraft)
- 1985: Mitsubishi sells design rights to Beech Aircraft Company
- 1985 to 1986: Beechcraft modifies aircraft for U.S. market
- 1986: First aircraft delivered as Beechjet 400
- 1989: Beechjet 400A introduced
- 2003: Beechjet 400A production ends
- 2004 to 2010: Hawker 400XP production
- 40+ years total platform life span: Across multiple corporate ownerships
The Diamond IA improvements specifically targeted Part 25 (transport category) certification requirements, with refinements to the Pratt & Whitney JT15D engines and aerodynamic adjustments. These 11 Diamond IA aircraft were later rebranded as the Beechjet 400 following the 1985 sale.
Why Mitsubishi Sold to Beechcraft
Despite the Diamond's solid engineering and reasonable market reception, Mitsubishi found it challenging to compete in the U.S. business jet market against established American manufacturers (Cessna, Learjet, Beechcraft) with their established service networks, dealer relationships, and brand recognition. The 1985 sale of design rights to Beechcraft allowed Mitsubishi to exit the U.S. business jet market while preserving the platform's commercial viability through Beech's distribution and service infrastructure.
Diamond Specifications
The MU-300 Diamond was a clean-sheet design with the following characteristics:
| Feature | Detail |
|---|---|
| Configuration | Low-wing twin-engine turbofan |
| Wing Type | Swept low-wing with high-aspect-ratio |
| Tail | T-tail empennage |
| Landing Gear | Retractable tricycle |
| Construction | All-metal aluminum |
| Engine Mounting | Rear fuselage |
| Cabin Cross-Section | Round, stand-up center aisle |
Cabin Interior
The Diamond cabin established the basic dimensions that would carry forward to the Beechjet and Hawker 400 family:
| Cabin Measurement | Value |
|---|---|
| Cabin Length | 15 ft 6 in |
| Cabin Width | 4.92 ft (59 inches) |
| Cabin Height | 4.75 ft (57 inches) |
Seating Configurations
- Standard 7-Passenger: Club seating with rear forward-facing
- 8-Passenger: With belted lavatory
- 9-Passenger Maximum: Various configurations
Performance
| Performance Metric | Value |
|---|---|
| Max Cruise Speed | 449 ktas |
| Long-Range Cruise | 410 ktas |
| Range | ~1,360 nm |
| Service Ceiling | 41,000 ft |
Engines
Two Pratt & Whitney Canada JT15D-4 turbofan engines, each producing 2,500 lbf of thrust (5,000 lbf total). The Diamond IA used the improved JT15D-4D variant with refinements to support Part 25 transport category certification.
Engine TBO: 3,500 hours (consistent with later Beechjet 400/400A).
Avionics
The MU-300 Diamond was delivered with analog instrumentation typical of late-1970s business jets. Available retrofits over the years have included:
- Collins Pro Line 4 (matching later Beechjet 400A standard)
- Garmin G600/G500 PFD upgrades
- ADS-B Out compliance
- WAAS/LPV navigation
Operating Costs
Operating economics are similar to the Beechjet 400A:
| Cost Item | Per Hour |
|---|---|
| Fuel (~160 gph) | $1,120 to $1,440 |
| Engine Reserve | $325 |
| Airframe Maintenance | $380 (challenging due to limited parts) |
| Misc Variable | $250 |
| Total Variable Cost | ~$2,075 to $2,395/hr |
Note: Original Mitsubishi-built Diamonds and Diamond IAs face parts supply challenges. Many operators have transitioned to using Beechjet 400A parts where compatible.
Pricing: A Specialty Market
| Variant | Pre-Owned Price Range |
|---|---|
| MU-300 Diamond (1978-1984) | $250,000 to $400,000 |
| Diamond IA (1984-1985) | $350,000 to $500,000 |
Note: The market for original Mitsubishi-built MU-300 and Diamond IA aircraft is highly limited. Most surviving examples were rebranded as Beechjet 400 following Beechcraft's acquisition.
Mission Profile
Best fit profiles:
- Aviation Collectors: Historically significant Japanese-built business jet
- Specialty Operators: Willing to manage parts supply challenges
- Lowest-Cost Twin-Jet Acquisition: Rare market sub-$500K twin-jet
- Owner-Operators With Mechanical Inclination: Self-supporting capability
Less suited if:
- You need OEM factory support (Mitsubishi exited the market in 1985)
- You require modern avionics out of the box
- You want a current-production successor (consider used Beechjet 400A or Hawker 400XP)
- You need predictable parts pricing and availability
Pros and Cons
What the MU-300 Diamond Does Well
- Historically significant first Japanese business jet
- Founding airframe of 40+ year Beechjet/Hawker platform lineage
- Twin-engine jet at very low acquisition cost
- Solid Mitsubishi-engineered build quality
- Same basic airframe and engines as Beechjet 400 (parts compatibility where modifications haven't diverged)
Tradeoffs to Understand
- Mitsubishi exited market in 1985 (no OEM support)
- Parts supply challenges (mitigated where Beechjet parts compatible)
- Very limited fleet (~100 total Mitsubishi-built aircraft, far fewer in operation today)
- Original avionics dated
- Specialty knowledge required for ownership
Frequently Asked Questions
Is the Mitsubishi MU-300 Diamond still supported?
Mitsubishi exited the business jet market in 1985 when it sold the design rights to Beech Aircraft Company. Some parts are interchangeable with the later Beechjet 400/400A (which Textron Aviation continues to support), but original Mitsubishi-specific components may be difficult to source.
How many MU-300 Diamonds were built?
Mitsubishi built 89 standard MU-300 Diamonds between 1978 and 1984, plus 11 improved Diamond IA aircraft between 1984 and 1985. The 11 Diamond IA aircraft were later rebranded as Beechjet 400 after the 1985 sale to Beechcraft.
What is the difference between MU-300 Diamond and Beechjet 400?
The Beechjet 400 is essentially the Diamond IA after Beechcraft acquired the design rights in 1985. The aircraft are very similar mechanically; subsequent Beechjet 400A and Hawker 400XP variants introduced increasingly significant improvements (higher MTOW, larger cabin, glass cockpit, etc.).
Why did Mitsubishi sell the Diamond program?
Mitsubishi struggled to establish a competitive U.S. business jet market presence against established American manufacturers with their domestic service networks and brand recognition. The 1985 sale to Beechcraft allowed Mitsubishi to exit while preserving the platform's commercial viability.
How far can a Mitsubishi MU-300 Diamond fly?
The MU-300 Diamond has an approximate range of 1,360 nautical miles.
Is the MU-300 Diamond single-pilot certified?
No. The MU-300 Diamond requires two pilots.
Can I get parts for an MU-300 Diamond?
Parts supply is challenging. Many components are interchangeable with the Beechjet 400 (Textron Aviation continues to support that platform), but original Mitsubishi-specific components may require extensive sourcing through specialty channels.
The Bottom Line
The Mitsubishi MU-300 Diamond and Diamond IA represent a historically significant moment in business aviation: the founding airframe of what would become a 40+ year platform spanning Mitsubishi, Beechcraft, Raytheon, Hawker Beechcraft, and Textron Aviation ownership. With only 100 total aircraft built and few remaining in active service, the Diamond is a specialty acquisition for aviation collectors and operators with specific expertise. For practical operating purposes, the much-more-common Beechjet 400A or Hawker 400XP (developed from the same platform) deliver substantially better support and operating economics.
Quantum Jets supports the platform across private jet charter, private jet rental, private jet card programs, aircraft purchase, jet purchase, jet sales, aircraft sales, aircraft management, jet management, private jet management, aircraft maintenance, aircraft refurbishment, fractional jet access, aircraft lease, and aircraft leasing structures.
Talk to a Quantum Jets broker for MU-300 Diamond market intelligence and acquisition advisory, including assessment of Beechjet parts compatibility and modification history.
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Mitsubishi MU-300 Diamond / Diamond IA Services from Quantum Jets
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Related Aircraft Guides:
- Beechjet 400A: Direct Successor (1990-2003)
- Hawker 400XP: Modern Successor (2004-2010)
- Cessna Citation II: Direct Competitor of the Era
Production of the Mitsubishi MU-300 Diamond and Diamond IA ended in 1985. All acquisitions are pre-owned and specialty. Specifications accurate as of 2026.