Indian airline Vistara issued an apology to Paralympic silver medallist Deepa Malik on Thursday after she complained about rude behaviour by a cabin crew member on a Mumbai-Delhi flight on Wednesday.

Malik complained to the airlines about "poor handling" of passengers in wheelchairs by the airline staff. In her on-board written complaint to the airline, she said that one of the cabin crew members behaved rudely with her when she was informing her mother on the phone that her flight was delayed.

"Crew member Priyanka was very rude in the flight. She told me to speak softly when I called parents to inform them about the delay in flight," she wrote in the complaint. "On objecting, she said 'sweetheart, chill'."

Malik also added that "wheelchair handling is so poor that you do not know how to shift a person from seat to cabin chair. The entire staff stands and looks at each other for 10 minutes. No action."

Vistara offered an apology on Thursday. They assured her of a proper probe and relevant action against the staff.

"As a team, we would like to sincerely apologise to Deepa for her disappointing experience. We have been in touch with Deepa and are grateful for the feedback shared by her. We are investigating the incident thoroughly and will take all necessary corrective actions to ensure something like this never occurs again," Vistara said in an apology letter to Deepa Malik.

Ms Malik later tweeted her appreciation towards Vistara for their response, and thanked them for their "sincere efforts".