The multi-million dollar Gulfstream IV took off from Teterboro Airport Thursday morning, and the pilot declared an emergency shortly after. We're told he attempted to land the plane in Albany, but aborted, and headed back to Teterboro where he he was able to bring it down safely.

A-Rod was not on board, and it appears the issue was mechanical.

TMZ obtained air traffic control audio, and you can hear the pilot mention a problem with a flap. Air traffic control opened a runway for the emergency landing, which was successful.

A source connected to A-Rod tells us the landing was made mostly as a precaution, and the pilot was making a test run. The FAA tells us it's investigating.

As we reported, A-Rod just took delivery of the G4 last month.