The Malaga Air Museum is well worth visiting and they offer both free admission and free car parking. However, if you are passing a couple of hours at Malaga Airport, it is possible to walk to the Museum despite the apparently pedestrian-unfriendly environment.
Equally, it is easy to walk from the Holiday Inn to the airport rather than taking the bus or, even more expensively, a taxi.
Walk out of the main terminal (T3) as if going to the Uber pick-up. Turn immediately right and walk along the outside of the terminal passing the booth selling coach tickets and a couple of shops/ cafes on the left. You are walking towards the Taxi pick-up point. (below)