Lufthansa cancelled 140 flights on Friday as pilots at its regional CityLine carrier neared the end of a 36 hour strike over pay.

Lufthansa, Europe's second-largest carrier, said it scrapped around 7 percent of its 2,000 daily flights. That brought the number of cancellations this week to 500, causing travel chaos for thousands of passengers.

The strike, which started at midnight local time on Wednesday, is due to end at midday.

CityLine operates around 400 of Lufthansa's 2,000 daily flights and feeds passengers into Lufthansa's Frankfurt and Munich hubs for long-haul routes.

The Vereinigung Cockpit union argues that CityLine pilots should have similar pay conditions as flight crew at Lufthansa's main passenger airline.

Lufthansa chief executive Wolfgang Mayrhuber said CityLine pilots are already earning more than their counterparts at other airlines.

Mayrhuber also told German newspaper Neue Osnabruecker Zeitung that he was concerned about the fragmentation of wage talks in the industry, a concern shared by other large German employers who fear triggering a wage spiral by dealing with a series of separate unions over pay.

Pilots at Lufthansa's Eurowings regional unit joined CityLine in previous strikes, but Lufthansa said earlier this week it was close to a deal with Eurowings after reaching an agreement with its Germanwings subsidiary.