The flight (AI 121) left IGI airport at around 1.45 PM after the delay in its departure was caused by wait for connecting passengers who arrived from different parts of the country, he said.
The spokesperson said the plane returned after the pilot calculated that if they go ahead with the journey, night curfew would be imposed at Frankfurt Airport and they would not be able to land.
Secondly, the flight duty time limitation of a pilot would have come into force as the flight was delayed. So the pilot decided to come back to Delhi, the spokesperson said.
The passengers were deboarded and given accommodation and the flight will now leave for Frankfurt tomorrow morning, according to the spokesperson.