In British English, collective nouns are can be used with a singular or plural verb:
1. The government have/has announced a new plan ...
2. Portsmouth (the football team) are/is in financial trouble again.
3. American Airlines are/is going ....
4. Lufthansa have/has decided to ...
In American English, the singular verb is preferred. I am not sure what the Americans would do with #3. I imagine they'd go for the singular, as 'American Airlines' is the (singular) name of the company.
Both BrE and AmE would use the plural if 'American airlines' referred to airlines which were American: Some American airlines are going ...