After the driver fainted, the bus veered off the highway north of Stockholm's Arlanda airport Sunday evening, the Swedish news agency TT reported.
"The driver's vision started to go black and then he fainted," said Benny Eriksson, chief executive officer of bus operator Ceris Resor.
Eriksson said once the driver realized what was happening, he had a colleague take the wheel, but the colleague was unable to prevent the bus from crashing into the ditch. Luckily, the bus had slowed down considerably before the crash.
The bus came to a stand still and then fell on its side, Eriksson said.
Some passengers suffered minor cuts and bruises, Eriksson said, but no one was seriously hurt.
"It was damn lucky that things went as they did," he told TT.