Passengers won't get a Maß, but they will be served by attendents in Blue Dirndl's for the women and Tracht for the men.

Details via lufthansa.com: Crew in traditional costumes to set the mood for Oktoberfest.
The uniforms are premiering today on a flight from Munich to New York and will be seen on flights from Munich to New York, Washington, Shanghi und Tokyo.
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"Lufthansa is thus not only setting the mood for the fifth Bavarian season, the 'Oktoberfest'. We also want to demonstrate that we feel at home at our southern hub and in Bavaria", said Karl Ulrich Garnadt, Group Representative and Head of Hub Management Munich.
In the history of Lufthansa, there was one other occasion when the uniform was replaced by traditional costumes: in 1957 the airline reported: “Lufthansa stewardesses in genuine Dirndls will serve passengers during the period of Munich’s ‘Oktoberfest’ from 17th September to 2nd October on flights from New York to Hamburg and the passengers from London to Munich from 21st September to 5th October“. On these routes, blonde female flight attendants wore light blue Dirndls, while their dark-haired colleagues wore pink dresses.
In the history of Lufthansa, there was one other occasion when the uniform was replaced by traditional costumes: in 1957 the airline reported: “Lufthansa stewardesses in genuine Dirndls will serve passengers during the period of Munich’s ‘Oktoberfest’ from 17th September to 2nd October on flights from New York to Hamburg and the passengers from London to Munich from 21st September to 5th October“. On these routes, blonde female flight attendants wore light blue Dirndls, while their dark-haired colleagues wore pink dresses.