Possible Clues:

• Their work sounds plain, and there's plenty of it at last (6)
• Delta force?
• They fly planes or guide ships
• At work they have an air about them - many of them, at last
• Stories about international airmen
• Shepherds very good, leading many
• Some American workers
• 'This is your captain speaking' speakers
• TV test episodes
• Ones doing loops and barrel rolls