To maintain a safe level of separation, the JetBlue aircraft halted its climb and leveled its altitude before eventually climbing again to cruising altitude. During communications between the aircraft and ATC, Curaçao‘s control center confirmed that the military tanker was not visible on their screens either.

With its transponder not switched on, the aircraft would also not have been visible to JetBlue‘s Traffic Collision Avoidance System (TCAS), which relies on transponder signals from nearby aircraft to warn of potential collisions. While this near-miss occurred during daylight hours, the situation could have been a lot worse if it happened at night during minimal visibility.

A JetBlue flight from the small Caribbean nation of Curaçao halted its ascent to avoid colliding with a US Air Force refueling tanker on Friday, and the pilot blamed the military plane for crossing his path.

“We almost had a midair collision up here,” the JetBlue pilot said, according to a recording of his conversation with air traffic control. “They passed directly in our flight path. … They don’t have their transponder turned on, it’s outrageous.”

The incident involved JetBlue Flight 1112 from Curaçao, which is just off the coast of Venezuela, en route to New York City’s John F. Kennedy International Airport.