A disaster could have taken place mid air when the captain of low-cost Dutch airline Transavia went out the toilet leaving the plane to the first officer.
Although in the incident happened in September, it was only made public yesterday by the Dutch safety board (OVV) in a report published on its website.
The body called it a 'serious' incident.
This is mainly because of the new rules by the EU. For instance, UK pilots can currently go up to 18 hours without sleep - but more than four out of ten pilots already report nodding off in-flight - of whom a third awoke to find their co-pilot also asleep.