You no-showed. Don't lose everything:

Why timing changes everything
Airline change fees and rules shift between cabins, fare buckets, and how close you are to departure. The same itinerary might be free to change at 11pm and $200 at 6am the next day. Always check the rules in the app before you call - the agent will quote whatever the system shows them, and you want to know in advance if they're missing a waiver. If your fare allows free changes, ask them to apply it instead of suggesting a paid one.
Do this right now
- 1Call airline within 2 hours, ask about 'flat tire rule' (US).
- 2Some airlines rebook for a fee if you call fast.
What you're entitled to

Self-service first, human after
App and website almost always rebook faster than a phone agent for simple swaps. Use the human channel for things the app can't do: split a booking, add a stopover, change names, or stack waivers. When you do call, have your booking reference, the new flight number, and a backup option ready. Agents move fast when the customer knows what they want.
Quick fixes that work
What to say at the desk
"I missed flight [X] due to [reason]. Please apply your flat tire rule and protect my onward segments."
Small things that make a big difference
- Check the airline's app first - new fares and seats appear there before phone agents see them.
- Same-day standby often beats a paid same-day confirmed change - ask both ways.
- If you booked through an OTA (Expedia, Kiwi etc), the airline may refuse to help directly. Loop both in.
- Screenshot the new fare before you commit - prices can change mid-call.
- Ask if any waiver applies (weather, schedule change, op upgrade). Agents won't always offer it.
Documents to keep handy
Have your passport, payment card, original confirmation email, and any travel insurance details open in tabs. If the change involves a visa-required country, double-check entry rules before you commit - airlines will not refund a ticket because you didn't know about a transit visa. A two minute check now saves a denied boarding later.