EasyJet founder Stelios Haji-Ioannou has threatened to sell his family's 37% stake in the low-cost carrier if it proceeds with what he describes as an "expansion-at-any-cost policy".
Haji-Ioannou has had a strained relationship with the carrier since quitting the board in 2010, when he accused management of pursuing rapid growth at the expense of shareholder value.
He reiterates that long-held view in an open letter published on 21 January, accusing directors of jeopardising the carrier's future with plans for an overly ambitious fleet renewal.
"I will be a loyal shareholder for the long-term provided management doesn't squander any more of our cash on new aircraft for at least the next four to five years," Stelios writes.
The Greek Cypriot tycoon sold 200,000 EasyJet shares last week in order to send a "clear message" to management. His brother and sister also sold the same amount, bringing the value of the family's holdings to about £1.3 billion ($2.06 billion).
"If the board places another order for aircraft, it will destroy shareholder value into the future," Stelios continues. "If they place such an order now I will be looking to dispose of more of my stake before this happens."
EasyJet has yet to make a final decision about its prospective fleet renewal, though management are believed to favour a strategy of continued expansion.
In his letter, Stelios accepts that higher airfares in recent years have boosted yields and benefited EasyJet's bottom line - doubling the value of the stock in 2012 - but he says this cannot be sustained if the carrier expands too quickly.
"Such price increases are only possible with a slow growth in fleet numbers," he insists. "It is because EasyJet has not bought more aircraft for some time that it is now doing so much better financially."
EasyJet shares were down 2.1% to 854p at the close of trading on 21 January.