Simplify the following text for a Grade 8 native English-speaking person.
Original: Lufthansa 's registered office and corporate headquarters is in Deutz , Cologne , with its main operations base ( Lufthansa Aviation Center ( LAC ) and primary traffic hub at Frankfurt Airport in Frankfurt am Main with a second hub at Munich Airport .
Simplified: Lufthansa is the largest airline in Germany , and the second largest in Europe . Some of Lufthansa 's hubs are Frankfurt am Main and Munich , A hub is an airport where people who fly from one city to a second city can transfer or change airplanes .