installation of Simviation freebees

Greetings friends,
I am sure this is an old chestnut, but when clicking on ' installation' on many of the sim freebees ( eg Alfa Lysander )I get the notice 'the application could not be installed because the AIR file is damaged. Try obtaining a new AIR file from the author '. Often the downloaded program does not detail a drop-list of individual programs to install manually. What can I do ?
regards
john lewendon
I am sure this is an old chestnut, but when clicking on ' installation' on many of the sim freebees ( eg Alfa Lysander )I get the notice 'the application could not be installed because the AIR file is damaged. Try obtaining a new AIR file from the author '. Often the downloaded program does not detail a drop-list of individual programs to install manually. What can I do ?
regards
john lewendon