Heathrow's biggest user, British Airways, has added to the wave of criticism being levelled at standards of service at the airport.
Over-crowding is one of the main concerns about Heathrow
Operator BAA has been criticised for over-crowding, delays and limitations on hand luggage at Heathrow.
BA's chief executive Willie Walsh said that problems at the airport had gone "well beyond" the levels that customers could be expected to put up with.
A Heathrow spokesman said millions were being spent on improvements.
Mr Walsh, whose airline is due to operate from Heathrow's Terminal Five when it opens next year, said that much of the flak was deserved.
"I agree with the criticism that has been levelled at the airport and we seriously need to address this," he told the BBC.
"It has gone well beyond the point at which we can expect our customers to put up with the standards."
He called on BAA to improve the quality at the airport, "not just in the interest of BA customers but of everyone using Heathrow".
His comments came after London Mayor Ken Livingstone said that Heathrow "shames" the city.
The airport was "typical of the English short-termism, lack of planning, lack of investment", he added.
The vice chairman of Standard Chartered Capital markets, Sir Thomas Harris, said that many executives now did whatever they could to avoid flying from or through Heathrow - including taking trains to mainland Europe to catch onward flights.
"We're trying to put a quart through a pint pot," Sir Thomas said.
The number of planes using the airport continues to grow
"This is an airport that was designed for about 45 million passengers and we're trying to put 68 million people through it.
"It's not surprising that any one element in a complex system at that airport, if it breaks down or deteriorates, leads to chaos and pretty appalling conditions."
And the government's City minister, Kitty Usher, said that business executives were becoming increasingly disenchanted with "Heathrow hassle".
"You spend so much time being processed," she said.
The UK is the only country in Europe which has retained restrictions on liquid in hand luggage - introduced after a terror alert last August. It also bans passengers from taking more than one piece of hand luggage on board.
The screening regime inconveniences passengers "with no improvement in security", claimed Giovanni Bisignani, director general of the International Air Transport Association, which represents the world's major airlines.
BAA had "failed to invest in appropriate equipment and staff to meet demand" he alleged.
On Tuesday, Ryanair boss Michael O'Leary said that standards at Stansted, another of BAA's airports, were "nothing short of appalling".
A BAA spokesman said that the company was currently spending millions of pounds to improve facilities at the airport and that Terminal 5 would open in March 2008.
"Over the next 10 years, £6.2bn will be invested in Heathrow," he said.
"And in May this year, the mayor approved the next big infrastructure project, called Heathrow East, which will replace our oldest terminal."
In March, BAA announced it was launching a scheme to end congestion and cut queuing time at its airports.
As part of its plans, BAA said it was spending an extra £40m to recruit 1,400 extra security guards and open 22 new security lanes across its seven UK airports.
It said that once complete, it hoped that this would reduce queuing to five minutes or less for 95% of the time.