You can but expect to be flagged by TSA and get the full search when you go through security. Buying an airline ticket on the same day is considered a security red flag.
Technically possible but you will pay lots and lots and lots more than had you booked in advance.
As a few before me have stated, I would book online. Not only are there many deals for booking even same day flights but many coupon offers to try as well. Many sites include hotel booking help so its easy to do everything in one shot.
Yes, you can. The fare will be based on availability. Also, most airlines based in the U.S. will add on a ticketing service fee for a ticket purchase at the airport or over the phone.
Yes, but like Austin said you'll pay more than if you just booked online. You may not be able to find a seat either because you're be booking day of, so save time and money and do it online in advance.
Always better to book in advance.
No.
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