Mach 3+ Oval, Lisburn, N. Ireland.Earlier this morning myself and my two sons were gardening. At 11:10 my eldest son aged 7 pointed at an aircraft and asked me what make of aircraft it was. It looked like an Airbus A321. He then asked why it was dragging a hot air balloon behind it. I looked up agian and noticed a small black oval, possibly 20 meters long and 10-15 meters wide which I would estimate was 1000-1500 meters behind the aircraft.For almost a minute the black oval maintained speed a distance from the Airbus, but it finally 'peeled off' at a speed of which I have never witnessed.I myself am a former Royal Naval Engineer and was designated to HMS Invincible (1993-1999). During this period I witnessed many military aircraft travelling at speeds in excess of Mach 1.8, usually at military exercises. If I compare the speed of the black oval to military aircraft I have worked with before, I would say it was accelerated from tailing the Airbus (400+ mph) to Mach 3.5 in 1 second.As you can imagine, at this speed the oval quickly vanished from site in the direction of Banbridge, SW.I do not wish you to contact me, but thank you for your time.((NUFORC Note: Witness elects to remain totally anonymous; provides no contact information. PD))