A Ryanair flight carrying 200 people was forced to turn back to Stansted after sticky tape used to 'patch up' the pilot's window came loose.
The Irish Aviation Authority (IAA) said the tape was being used merely as an extra precaution to secure a new window seal.
But the pilot made the decision to terminate the flight after the tape became loose and started making flapping noises.
One passenger, Anthony Neal from Kent, told The Sun: 'We were kept in the dark, and were terrified. I could see guys taping in the windscreen with what looked like duct tape or gaffer tape.
'We were in the sky, then the pilot said due to damage on the windscreen, we were going to have to turn back.'
Ryanair has insisted that normal procedures had been followed and that there was no danger to passengers or crew.
A spokesman said: 'We do not comment on routine technical issues. All Ryanair flights operate in accordance with approved safety standards.'
The news comes as Ryanair boss Michael O'Leary outlined expansion plans that could see passenger numbers almost double across Europe.
The Irish businessman revealed that he is in talks with plane makers Boeing, Comac in China, and Irkut in Russia to buy between 200 and 300 new aircraft.
Discover the world's worst airlines below: