Heathrow Airport has been rated poor for disabled travellers in a report from the UK's aviation regulator.
Some passengers were not treated with "dignity and respect" with waits of one to two hours to get off planes, the Civil Aviation Authority said.
Manchester, East Midlands and Exeter airports also received the low rating, but 26 airports were given a good or very good rating.
Heathrow said it was addressing the issues raised in the report.
'Make your own way'
The CAA highlighted a survey of about 1,200 passengers requiring assistance at Heathrow, where 62% rated the service poor or very poor.
The regulator said: "There have been instances of unacceptable levels of customer service where passengers' needs have not been met and, in some instances, where passengers have not been treated with dignity and respect.
"Substantive issues still exist with the quality of the assistance service provided at Heathrow."
The regulator admitted Heathrow, the UK's largest airport, had "certain challenges" like long walking distances.
But journeys for passengers with mobility issues would often take "significantly longer", and the airport's contractor Omniserv "encouraged passengers to make their own way through the airport because of a lack of staff or equipment".
Waits of up to two hours for help when getting off flights were recorded on a number of occasions, the CAA said.
The report acknowledged that management at Heathrow, alongside Omniserv, are implementing an improvement plan to reduce waiting time and service quality issues.
A spokeswoman for Omniserv said the company is "investing significant sums in staff training" and will "continue evaluating our performance... to provide the best service to all of Heathrow's passengers".
Heathrow said it was "extremely disappointed" by the CAA's findings and apologised to customers affected.
A spokesman added: "[The findings of the report] are not acceptable and fall short of the experience Heathrow aims to provide its passengers.
"Addressing the issues raised in this report is a priority for us. We apologise to those who have been affected and are taking action."
The CAA said the other airports rated poor - East Midlands, Manchester and Exeter - had not consulted disability organisations, or set up focus groups to receive feedback from service users.
East Midlands Airport also experienced "unacceptably long waiting times", according to the report.
Last year a wheelchair user was left stranded at the airport because staff had "forgotten about him".
Paddy Costello, 62, was supposed to be getting a Ryanair flight to Ireland, but his flight left without him.
At the time an airport spokesman said: "As soon as we were made aware of the situation, we reacted quickly by aiding the passengers in re-booking flights and offering an overnight stay in a premium hotel on site."
Although four airports were rated poor, the aviation regulator was encouraged to see a 66% increase in the number of travellers requiring assistance since 2010.
In 2016 three million passengers with mobility issues flew through British airports and CAA consumers director Richard Moriarty said: "UK aviation should be proud that it continues to serve a rapid increase in the number of passengers with a disability."
Birmingham, Glasgow and Glasgow Prestwick, Humberside, Inverness and Norwich airports were all rated very good.
The report said: "Norwich, in particular, has created excellent partnerships with local disability organisations, especially those representing people with 'hidden disabilities'."
The airports rated good were: Aberdeen, Belfast City, Belfast International, Bournemouth, Bristol, Cardiff, City of Derry, Doncaster Sheffield, Edinburgh, Leeds Bradford, Liverpool, London City, Gatwick, Luton, Southend, Stansted, Newcastle, Newquay, Southampton and Sumburgh.