A deranged Westchester man was arrested at La Guardia Airport yesterday after he was spotted walking on the tarmac near a US Airways jet just minutes from takeoff, sources said.

The startling safety breach, the latest in a string of blunders at local airports, occurred just before Flight 1909 was due to take off for Charlotte at 1:05 p.m., the sources said.

The pilot spotted Andre Reid, 21, of Mount Vernon, walking by the Airbus 321 “like he was taking a stroll in his back yard,” said one police official.

The pilot became “spooked” and opted to “dump” the flight — meaning all the passengers and their luggage were taken off the plane and rescreened.

Cops charged Reid — who had walked through a door to the tarmac without being questioned — with trespass.

The incident delayed the passengers’ departure by at least 90 minutes.