BERLIN (Reuters) – German flag carrier Lufthansa said on Friday it had to reduce the buy-on-board meal offer for some short- and medium-haul routes departing from Frankfurt as its catering contractor Gate Gourmet struggles with staff shortages. “This means our (catering) offer is currently not available in economy class on these Lufthansa flights to and from Frankfurt. The offer in business class and on long-haul flights is not affected,” a Lufthansa spokesperson said in a statement. A spokesperson at Gate Gourmet’s owner GateGroup said the issues are limited to a small number of flights depar…