Two F-35B aircraft fly in close formation while in short takeoff/vertical landing mode for the first time last week. Pilots Peter Wilson and Dan Levin flew the test jets in STOVL mode, also known as Mode 4, with the F-35B LiftFan engaged and engine rotated downward. The mission measured the effects the aircraft had on each other while in Mode 4 to ensure they can operate in formation safely in an operational environment. The U.S. Marine Corps plans to declare Initial Operating Capability with the F-35B next year. The F-35 Lightning II is a 5th generation fighter, combining advanced stealth with fighter speed and agility, fully fused sensor information, network-enabled operations and advanced sustainment. Three distinct variants of the F-35 will replace the A-10 and F-16 for the U.S. Air Force, the F/A-18 for the U.S. Navy, the F/A-18 and AV-8B Harrier for the U.S. Marine Corps, and a variety of fighters for at least 10 other countries.