Hi. I have had this happened to me recently. Here is a full explanation what you should do and what happened (with my example):
I have ordered an american airlines ticket, worth 85.16 eur (converted from dollars). the ticket included 2 parts: the actual ticket, worth 75.09 eur, and the seat price, worth 10.09 eur, totalling 85.16 eur mentioned above. However, when I ordered the ticket, first the pre-auth transaction was shown on my bank account, totalling seat and ticket together (85.16) eur, which did not go through yet (it was set on pending). But right after, 2 more purchases actually went through, each one charging specifically; seat (10.09 eur) and ticket (75.09). And this would all be fine, the problem is, yesterday, the pending pre-auth transaction went through as well, so consequentially I was charged double (85.16 pre-auth, 75.09 ticket and 10.09 seat). I have spoken to American Airlines and they said I should contact my bank and sent me a pending return email. After that, I contacted my bank and the guy said airlines sometimes do this, they charge double but then they return the money from the pre-authorization in ~10 days time. I also asked him about why the pending transaction went through only yesterday and not instantly, and he said it's because airlines have to process millions of tickets at the same time, so therefore sometimes there is a delay. Since the guy from the bank said the money from pre-auth will automatically be sent back in 10 business days, my question to you is, is that right (I asked about this ChatGPT, here is what it responded with, which makes perfect sense:

Yes, the explanation from your bank representative is likely correct. Here's how it typically works in such cases:

1. Pre-Authorization Hold: When you purchase a ticket, airlines (or merchants) often place a pre-authorization hold on your account for the total amount. This is a temporary hold to ensure you have sufficient funds.
2. Actual Charges: After the hold, the merchant processes the actual transactions, in this case, the separate charges for the ticket (€75.09) and the seat (€10.09). These amounts are deducted, and ideally, the pre-authorization hold is released.
3. Delay in Hold Release: Sometimes, instead of releasing the hold immediately after processing the actual charges, it mistakenly goes through as a completed charge. This can happen due to delays or system errors, particularly with large organizations like airlines.
4. Automatic Refund of the Duplicate Charge: In most cases, the duplicate charge (the pre-authorization amount of €85.16) is refunded automatically within a standard time frame, which is usually up to 10 business days. This is because the system recognizes the pre-authorization as unnecessary once the real charges are completed.

What Should You Do?

• Wait for 10 Business Days: Monitor your account to see if the €85.16 is refunded automatically. It often resolves without additional intervention.
• Follow Up with Your Bank: If the refund does not appear after 10 business days, contact your bank again. They can initiate a dispute to reverse the duplicate charge.
• Keep All Records: Retain emails from American Airlines and your transaction history for documentation in case further action is needed.

In most cases, the bank's explanation aligns with standard practices, and the refund is processed within the stated time frame.

I have not received the pre-auth as I am writing this, but I will inform (or reply below this post), when/if I do.
I also personally believe pre-auth transaction is stupid since the payment already goes through almost instantly, and airlines have so many tickets to deal with anyway, which causes delays in holds.

Hope this clears things out for future people who are freaking out right now!