Thousands of European passengers were left stranded on planes to nowhere on the tarmac for hours last Monday after a technical glitch in air traffic control in the UK. Many wondered why they couldn't get off the plane. Experts explained the problem on Sky News .

Imagine you've boarded the plane, buckled your seatbelt, and put your phone on airplane mode. But then the flight is delayed, and you have no idea when you'll leave the runway or how long you'll have to wait.

It is a familiar experience for many passengers. Through the thick oval glass panels, you can see the airport terminal. Sitting inside the terminal but being delayed is still much more comfortable than sitting in the cabin.

So why can't passengers get off the plane and go back to the terminal to escape the uncomfortable crowding?

An aircraft can only be given a slot at an airport at a certain time, explains Sean Tipton, a spokesman for the Association of British Travel Agents (ABTA). The aircraft needs to be ready to take off when a slot is available.

It takes time to get people off the plane and the boarding process will need to start over to make sure everyone gets back on the plane. During that time, the flight may be lost.

“This will cause potentially longer delays,” Mr Tipton said. “So it’s obviously very frustrating to have passengers sitting in a cabin on the tarmac for two or three hours, but it’s “really for the convenience of passengers.”

In Europe, regulations require passengers to be given the option to disembark after they have been on the tarmac for five hours. It is rare for tarmac delays to last that long, Tipton said.

Additionally, airlines are obliged to provide reasonable refreshments if a flight is delayed for more than 2 hours...