The malfunction was first noticed at noon on Wednesday, and was only fully corrected during the early hours of Thursday morning.
According to airport operator ANA, a total of 64 flights were cancelled, a further 11 diverted to other airports, while 322 suffered delays.
Many were allowed to depart after midnight, overriding the limitations of a law limiting noise over the capital. It is estimated that 50,000 air passengers were affected by this unprecedented problem at Portugal’s largest airport.