Best Credit Card For Air Travel

I just started a new job with lots of air travel and hotel stays. We pay fees in advance and then reimbursed the money. I'm just wondering what your experience is the best program or credit card (preferably with no annual fee) to earn flyer miles and / or free nights? Thank you in advance!

Me prefers the Discover Card
you can earn more frequent flyer miles, but you must use the card frequently
more you use most, you can win
it may be useful

Since the credit card company is obliged to pay someone for the awards are not very good with no-fee cards. If you use the card to pay for business travel you may be able to deduct the tax on your taxes. I have the Amex Membership Rewards and love it, especially using the points on many airlines.

I also have questions for my credit card. I posted my question on wish123 and received a reply from an expert who has solved my problems. Highly recommend the site.