The American moguls also run the NFL franchisee and were in action on home soil as they took on the Philadelphia Eagles on Monday night.
The Buccaneers were beaten 25-10 in the NFC Division clash, but that was the least of the Glazer family's problems.
Footage showed a plane flying over the Raymond James Stadium in Tampa Bay with "#GlazersOut" printed on a banner.
It is the latest in a number of protests staged by supporters of the Premier League giants.
United fans want the Glazers to sell up after 18 years of perceived mismanagement.
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The club had been put up for sale in 2022, with big-money interest from two major parties.
Qatari banker Sheikh Jassim Bin Al Thani and British billionaire Sir Jim Ratcliffe both submitted bids worth around £5billion for full control of the club.
But there has been little movement and plans to sell the club are in huge doubt, much to fans' frustrations.
The banner was organised by the United Pittsburgh and Tampa supporters groups.
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Fans will be hoping that their protests could be enough to force the Glazers into a sale, but based on the evidence so far, that might be a tad ambitious.