But if you forgot, it's OK. Most airlines, Keyes said, allow travelers to request miles three to 14 days after booking and within 12 months of travel.

Yes, most airlines allow you to claim frequent flyer miles retroactively if you forgot to add your loyalty number at the time of booking or check-in. The window for making a claim typically ranges from 6 to 12 months after the flight, though some airlines allow you to claim miles for flights taken up to 30 days before you even joined the program. To do this, you usually need to log into your account and navigate to a "Request Missing Miles" or "Claim Past Flight" section. You will need your ticket number (a 13-digit code starting with the airline's specific prefix) and your flight details. It is highly recommended to keep your physical or digital boarding pass until the miles appear in your account, as the ticket number is often only found on the receipt or the pass itself. Once submitted, the miles usually take anywhere from 48 hours to a few weeks to be verified and credited to your balance.

Yes, it is often possible to retroactively claim frequent flyer miles for past flights, but the process and eligibility depend on the airline’s policies. Here’s how you can typically go about it:

1. Check the Airline’s Policy

• Each airline has its own rules regarding retroactive mileage claims. Some allow claims for flights taken within a specific time frame (e.g., 6 months to 1 year), while others may not permit retroactive claims at all.
• Review the airline’s frequent flyer program terms and conditions on their website.

2. Join the Frequent Flyer Program

• If you weren’t already a member of the airline’s frequent flyer program when you took the flight, you may need to sign up first. Some airlines allow you to retroactively credit miles to your account after joining, but this varies.

3. Gather Your Flight Information

• You’ll need details such as:
  • Flight number(s)
  • Date(s) of travel
  • Booking reference or ticket number
  • Receipts or boarding passes (if available)

4. Submit a Claim

• Most airlines have an online form or process for retroactive mileage claims. Look for a section like “Missing Miles” or “Retroactive Mileage Request” on their website.
• If an online form isn’t available, you may need to contact the airline’s customer service directly.

5. Wait for Processing

• After submitting your claim, it may take several days or weeks for the airline to verify and credit the miles to your account.

6. Consider Alliance Partners

• If you flew with a partner airline within the same alliance (e.g., Star Alliance, SkyTeam, or Oneworld), you may be able to credit the miles to your frequent flyer account with your preferred airline.

Tips:

• Act quickly, as some airlines impose strict deadlines for retroactive claims.
• Keep all travel documentation in case you need to provide proof.

Examples:

• Delta SkyMiles: Allows retroactive claims for flights taken up to 9 months prior.
• United MileagePlus: Permits claims for flights up to 12 months prior.
• American Airlines AAdvantage: Typically allows claims for flights within 12 months.

Always check the specific airline’s policy to confirm eligibility and deadlines.