The plane was reportedly organised by a Facebook group of fans called Football Forum.
Despite initially appearing to show gratitude to sacked United manager David Moyes, the message is believed to be a sarcastic one, with the ex-Everton manager's 10-month tenure widely ridiculed by supporters.
The Scot led United to their worst ever Premier League points tally, and also failed to qualify for the Champions League, despite spending over £60 million on Marouane Fellaini and Juan Mata.
And one of the organisers of the stunt told the Times of Malta that all the fans who paid for the plane were fans of rival clubs who had “enjoyed Moyes as manager.”
A similar message, paid for by United fans, was flown over Old Trafford during the club's 4-1 win over Aston Villa in March, reading “Wrong one – Moyes out”.