Wiktionary
n. The first flight of an airplane or other airborne vehicle, usually used to test or demonstrate the functions of the systems.
Wikipedia
The maiden flight of an aircraft is the first occasion on which an aircraft leaves the ground under its own power. This is similar to a ship's maiden voyage.
The first flight of a new aircraft type is always a historic occasion for the type. In the early days of aviation it could be dangerous, because the exact handling characteristics of the aircraft were generally unknown. The first flight of a new type is almost invariably flown by a highly experienced test pilot. First flights are usually accompanied by a chase plane, to verify items like altitude, airspeed, and general airworthiness.
A first flight is only one stage in the development of an aircraft type. Unless the type is a pure research aircraft (such as the X-15), the aircraft must be tested extensively to ensure that it delivers the desired performance with an acceptable margin of safety. In the case of civilian aircraft, a new type must be certified by a governing agency (such as the Federal Aviation Administration in the United States) before it can enter operation.
Usage examples of "maiden flight".
A hush fell over the assembled gnomes, giving the maiden flight-and first field test-of the new and improved Unquenchable a near-religious significance.
With his usual flair for publicity, Sir Lawrence arranged for her maiden flight to commence on the hundredth anniversary of Sputnik Day, 4 October 2057.
And between the orbits of Earth and Venus the most famous of all comets would meet the still uncompleted space-liner Universe, on her maiden flight.
No use risking overcontrol on his maiden flight, wallowing all over the sky like a shot duck.
She pushed herself on this maiden flight, past the first ache of her wing muscles, until the legs that would help her land cramped as well.