The Dutch airline KLM has offered “sincere apologies” to a Paralympic athlete who was denied access to an onboard wheelchair during a long-haul flight so she could go to the toilet.

The cabin crew on the flight later called the police after the request from Hannah Babalola, 37, who is paraplegic and competes in track events, for the wheelchair, known as an aisle chair as it is narrow enough to be used inside a plane. They first handed her a written notice, headed: “Unacceptable conduct and final warning on behalf of the captain of this plane.”

The incident happened on 26 May, when Babalola, who competes for Nigeria and lives in Chicago, was returning home from a wheelchair-racing event in South Africa.

She had booked the KLM return flight from Chicago to Cape Town, via Amsterdam, as a wheelchair-using passenger. The outbound flight went smoothly, but as she began her return journey she was taken to the plane by wheelchair and asked by cabin crew, once she had boarded, if she would require an aisle chair during the flight. When she said she would – the flight to Amsterdam was almost 11 hours – the problems started.

In a conversation with cabin crew and the captain that she asked permission to record, which was shown to the Guardian, a crew member can be heard saying they could not accept a passenger in need of an onboard chair as it was too dangerous to use during a flight in case of turbulence and that Babalola’s two options were to go to the toilet without using the wheelchair or to “offload” from the plane.

“I needed to get home to Chicago to my family and to get to work and I couldn’t ‘offload’ from the flight,” Babalola said.

Security was called by the cabin crew but declined to take any action against Babalola. When the flight landed in Amsterdam, the crew asked the police at the airport to be on standby, but they too declined to take action.

Babalola transferred to a different connecting flight in Amsterdam to complete the journey to Chicago.

She said: “I felt compelled to avoid eating or drinking for the duration of the flight because I feared needing to use the restroom and being unable to access it. I spent much of the flight trying to control my emotions and I found myself crying because of the way I had been treated.

“This experience was humiliating, distressing, and degrading. The situation caused me significant physical discomfort and emotional distress. I believe that the manner in which I was treated raises serious concerns regarding discrimination and equal treatment. All passengers, regardless of disability or personal circumstances, deserve to be treated with dignity and respect.”

Babalola made a formal complaint to KLM about her experience.

A member of KLM’s customer service staff replied, stating: “It is very concerning to read about this experience, particularly the distress caused during boarding and throughout the flight. Your account describes a situation that must have felt deeply upsetting and unsettling, especially when travelling with an accessibility need and simply expecting appropriate assistance and respectful treatment.”

They added: “A full review of the circumstances should now be carried out by the appropriate teams. This will typically include examining the reports submitted by the crew and any other relevant information available in relation to the flight. My sincere apologies are extended for the distress and upset this experience has caused.”

The British Paralympian Anne Wafula Strike hit the headlines in 2017 when she was forced to wet herself on a train. The incident triggered a national debate about equal access to transport for people with disabilities.

She said: “Nine years ago I was forced to wet myself on a train because there was no functioning accessible toilet. Almost a decade later, the experience of Hannah Babalola shows we still have a long way to go. It is upsetting that disabled people are having to fight the same battles over and over again just to access the rights that able-bodied passengers have.”

A KLM spokesperson told the Guardian: “We regret that an incident occurred involving one of our passengers on the flight from Cape Town to Amsterdam on 26 May. Out of respect for the privacy of both the passenger and our crew, we find it inappropriate to discuss the details of the situation.”