What counts as a source
- Regulations: the Code of Federal Regulations, Title 14 (Aeronautics and Space), read on the official eCFR at ecfr.gov. Each page names the parts and sections it relies on.
- Federal notices: the Federal Register, read on govinfo.gov.
- DOT publications: the Air Travel Consumer Report and the Airline Cancellation and Delay Dashboard on transportation.gov.
- International rules: ICAO for Montreal Convention liability limits.
- Airline policies: each airline's own fee pages and contract of carriage.
- Company status: SEC filings, e.g. Spirit Airlines' May 2026 Form 8-K.
We don't use blogs, aggregator tables or AI summaries as the source of a number. If a secondary source is the only way we could read something, we name it and say so on the page.
How bag fees are recorded
- Fees are per person, per direction, for standard-size bags under the weight limit, in standard economy, on domestic routes unless stated.
- When an airline changes fees, it usually dates the change by when the ticket was bought. We keep the old and new tables and the calculator chooses by your purchase date.
- "Online / airport" pairs are kept separately. For JetBlue, the "within 24 hours" price is JetBlue's listed price plus the saving JetBlue says it includes; we say so on the page.
- If a price isn't published as text (United's second and later bags appear only in United's own calculator), we leave it blank rather than copying a number from a news story.
- Status, credit-card and military waivers are listed but not applied to the calculator.
Gaps and blocked pages (Oct 29, 2026)
- transportation.gov and flightrights.gov refused our reader (an automated-access block). We read the DOT dashboard and complaint figures from search-engine copies and a third-party tally, and say so where they're used. The regulations themselves were read on eCFR.
- Sun Country's fee page blocked our reader, so we publish no Sun Country prices.
- Frontier and Allegiant don't publish fixed checked-bag prices; both say prices vary by route and date. We show what they do publish (weight limits, overweight fees).
- Spirit Airlines' own sites didn't load. Its status comes from its SEC filing.
- ICAO's treaty PDF refused our reader. Montreal Convention Article 31 deadlines are quoted from a U.S. federal court opinion on govinfo.gov.
How rules are summarized
Guides say what a rule requires and quote the operative words. They don't predict how a particular dispute will turn out, and they aren't legal advice. Where an airline promise (like a meal voucher) isn't a legal requirement, we say it's a commitment, not a rule.
Updates
Each page shows the date its sources were last checked. When a source changes we update the figure and the date; we don't silently overwrite older fee tables that still apply to tickets already bought.
Posts from X
We count public posts on X with X's own search counts and quote a few, linked, to show what people run into. Counts are for English-language posts, exclude reposts, and cover the date range stated next to them. We don't use them as evidence of what a rule says.