F-4 Phantom II: Mach 2.23, but a Vietnam Letdown

The McDonnell Douglas F-4 Phantom II was the fastest fighter jet of its day, hitting Mach 2.23 with two General Electric J79 afterburning turbojets producing over 17,000 pounds of thrust each. Simple Flying reports that the aircraft set 16 in-flight performance records, including a sustained altitude of over 66,443 feet in 1961. Even nearly 70 years after its first flight in 1958, the F-4 outruns modern jets like the F/A-18 and F-35.

Speed that came at a cost

The F-4 was designed as a high-altitude interceptor, meant to kill enemy planes with missiles from beyond visual range. Engineers left off a gun, figuring dogfighting was obsolete. That proved disastrous when the Phantom entered Vietnam War air combat in 1965.

"Its radar had difficulty differentiating between friendly and enemy aircraft, forcing pilots to engage in close combat with hostiles."

Once the missiles were fired, the F-4 was defenseless. Smaller MiG-21s outmaneuvered the bulky Phantom, and pilots lacked training for short-range fights. Simple Flying notes the F-4 was shot down at alarming rates in its early Vietnam days.

The fix came too late

External gun pods were added but were inaccurate. The internal Gatling cannon on the F-4E variant, along with leading-edge slats that improved maneuverability, helped, but the aircraft remained an interceptor adapted for a role it wasn't built for. Later F-4S models got smokeless engines, but the damage was done.

How the F-4 compares to other fast US fighters

Simple Flying lists the top speeds of American-built fighter jets:

• McDonnell Douglas F-15 Eagle: Mach 2.5
• General Dynamics F-111 Aardvark: Mach 2.5
• Grumman F-14 Tomcat: Mach 2.34
• Lockheed Martin F-22 Raptor: Mach 2.25
• McDonnell Douglas F-4 Phantom II: Mach 2.23

The F-15, designed from the ground up as an air superiority fighter, easily bested the F-4 in testing and has a perfect combat record with 104 victories and zero losses.

The lesson

The F-4 Phantom II was a bold bet on long-range missile combat that didn't account for close-in dogfighting. Nearly 5,200 were built between 1958 and 1981, making it the most-produced American supersonic fighter. But speed alone couldn't win the war.

• Cold War
• F-4 Phantom II
• fighter jet
• Mach 2.23
• McDonnell Douglas
• top speed
• Vietnam War