Charged twice for same flight? Is this common?
 

Did it error out the first time you tried to purchase? That will cause two authorizations.

Using a debit card for an airline ticket purchase is typically not a great idea, especially given the proliferation of credit cards that provide bonus points earning and/or travel insurance benefits.

Huh. Sounds like a UA error. I've gotten multiple authorizations for a single ticket before, the one that's pending should drop off eventually.

You know you can use your Sapphire for Apple Pay, right?

Using a debit card (in credit card mode) for any purpose isn't a good idea, for exactly this reason: you set yourself up for merchant mistakes or a compromised card causing you grief, which include possible inability to withdraw cash when you need it, or even to have checks bounce.

The other thing is there's no fraud protection. If your account is compromised, the bank has no obligation to make good the loss.

I was charged twice recently and called in. The agent I spoke to said she coudn't touch the payments associated with the reservation but that they would drop off in a few days. And they did.

To the core question, are multiple credit authorizations common, the answer is they are not uncommon. And as others have mentioned, they excess authorizations will eventually delete and you have not been double charged.

It is a consequence of using debit cards that authorizations limit your purchasing ability -- and this will happen with other vendors. Buying auto fuel, renting a car, checking into a hotel, .... will all have nasty surprizes with a debt card.

Some of us with poor credit ratings only have debit cards as an option to purchase something.

Very common, and yet another reason not to use debit cards.

While UA is not insolvent and not likely to cease operations in the next few days, there have been a number of air carrier bankruptcies in the past 2-3 years and there may yet be some more in the near future.

For US-based travelers, with a CC, you have absolute statutory protection. On a debit card, you are likely an unsecured creditor which means that you may possibly see a few pennies on the dollar in a couple of years. Do not ever use anything other than a CC to pay for any service to be rendered in the future, e.g. air tickets, prepaid hotels, cruises, tours and the like.

This is entirely separate from the "hold" problem which can easily tie up a small fortune.

... which would make a debit card problem all the worse if it were to happen: bounced checks, no cash, no ability to buy essentials such as food, and no credit card to fall back on.

looks like there was an pre- authorization send to your credit card company twice , this happens sometimes when you buy something via UAL.COM I had this a couple of times w UA before and the first pre-charge was released within 24-48hrs ....so check your CC again in a day or so ...
Was told from from an UA agent this happens sometime when UA.com (web) tries to issue a ticket while you still in your Reservation ....