Soaring temperatures grounded a fleet of buses in the East Midlands after some roof panels fell off.
Trent Barton Buses, which cover routes in Notts and Derbys, took almost 30 buses out of service on Wednesday.
Ceiling panels on two buses dropped off after their adhesive melted, prompting bosses to bring the whole fleet into the garage for safety checks.
The buses - manufactured by Wrights - are all less than a year old and still under guarantee.
"It is a drastic thing to do (taking buses out of service) and people had to change buses in mid-route," said Trent Barton's Melvyn Hopwood.
"I am sure they will understand that you cannot take a risk where safety is concerned."
Nobody was hurt and Trent Barton says the ceiling panels have been replaced.
Passengers were forced to travel on older buses while the checks were carried out.
The company says despite the continuing high temperatures, they do not expect a repeat of the problem.