FRANKFURT, August 4, 2008 (AFP) - The head of the German trade union Verdi said Monday he would reimburse a free first-class holiday ticket to Los Angeles with Lufthansa used a few days before union members staged a strike at the airline.

'I underestimated the importance of this flight in public opinion,' Frank Bsirske told the popular daily Bild. 'It was wrong' to make such a trip, while Verdi was calling for a strike against Lufthansa to press for higher wages.

As vice president of the airline's supervisory board, Bsirske is entitled to free tickets, he noted.

As a result, he left on vacation with his wife for the US city, from where he continued on to a South Pacific island destination.

A few days later, Lufthansa ground personnel and cabin crews walked out on strike, forcing the carrier to cancel hundreds of flights.

'I have asked the supervisory board's administration to bill me in full for the flight,' said Bsirske, who is still on holiday.

Over the weekend, calls for his resignation had multiplied, and he was also criticised by the union's rank-and-file.

Verdi member Michael Wendl from the southern state of Bavaria was quoted by the magazine Der Spiegel on its website as saying that Bsirske had demonstrated 'a basic political lack of judgement.'

It showed that 'you want to get closer to the top management and belong instead of having your ear tuned to the base.'

The Lufthansa strike ended last week after the union and management reached a compromise on staff demands for a pay hike.