HYDERABAD: A 20-hour layover at the Frankfurt airport has disrupted the onward travel plans of most passengers after their Hyderabad-bound Lufthansa flight was denied permission to land at Rajiv Gandhi International Airport here.

The flight LH752 departed Frankfurt at around 2:30 PM on Sunday and was originally expected to land in Hyderabad at 6:00 AM on Monday. However, the non-stop flight was diverted back to its origin airport due to a "bomb threat".

"After three hours of journey (on Saturday) the passengers were informed that the flight had no permission to land at Hyderabad Airport and hence the aircraft was going back to Frankfurt. All our onward journey plans were upset. I have to go see my parents who are very old," Madhvi Latha, a passenger on the flight, said here.

She said she had to go further to Guntakal in Andhra Pradesh.

Another passenger, Venu, who was travelling from San Francisco, expressed shock over the turnaround and said his flight was airborne for nearly four hours before it returned. His onward journey resumed only around 10 am the next day, significantly delaying his arrival in Hyderabad.

"They told us that the flight is going to return. We didn't understand. It was a shock for us that the flight was coming back. It was a shock when they told us that the flight was going to return. We did not understand what was happening," Venu said, expressing relief that all passengers were safe.

The disruption caused even longer delays for some passengers.

Arogyam Chowdhury, who originally had flown from Canada, experienced the longest delay in the group with his layover in Frankfurt lasting nearly 72 hours.

Another passenger Anay, a school boy, recalled watching inflight TV when the announcement was made that the plane was returning to Frankfurt.

According to Hyderabad Airport sources, a bomb threat email targeting Lufthansa flight LH 752 was received at the Hyderabad airport at 18:01 hrs on June 15.

They said a bomb threat assessment committee was formed and all procedures were followed as per standard operating procedure. In the interest of safety, the airline was advised to divert back to the origin or the nearest suitable airport.

Flight LH 752 operated by a Boeing 787-9 Dreamliner aircraft departed from Frankfurt at 14.29 hours instead of its scheduled departure time of 13.05 hours, as per flight tracking website flightradar24.com.