The transatlantic city grid

What one row is

One row is one US gateway metro, one European city, and the lowest round-trip economy fare found on Google Flights for a one-week trip departing within six months of August 30, 2026: one adult, taxes included, checked bags excluded. Every cell was priced twice that day and the lower reading kept. The figure is a floor across a window, so it tells you what a good fare on that pair looks like; it does not tell you what any particular date costs.

Origins are metro areas rather than single airports, because that is how a traveler shops. Destinations are cities for the same reason, and a code such as LON covers every airport in the city. The site's airport pages take the individual airports apart where it matters.

A look at the file

Data dictionary

The same definitions travel inside the JSON file, so a download stands on its own.

Coverage

Limitations, stated

• Floors, not fares. Each figure is the lowest found across a six-month window. Most dates in that window cost more.
• One source. Every fare comes from Google Flights. We measure how far it disagrees with a second source on a sample and publish the result on How we review, rather than blending two sources and losing comparability.
• Off-season window. The current snapshot covers departures from early fall to late winter. Summer is a different market.
• Economy only, bags excluded. A carrier that charges for the first checked bag looks cheaper here than it is for anyone traveling with one. The carrier grid records which airline set each floor, and this file does not.
• A snapshot. One day's collection. It supports a statement about that day and the window it priced, not a statement about how the market moves. The month-over-month view needs the archive, which is not distributed.

License and citation

Common questions

Why is each fare the lower of two sweeps?

Because the figure is defined as a floor: the lowest fare found for a one-week trip anywhere in a six-month window. The minimum of two same-day samples is simply a better estimate of a floor than one sample is, and because every cell was sampled exactly twice, no city gets a better shot at a low reading than another. A higher second reading never raises a floor already observed.

Why are New York and Washington metro codes rather than airports?

Because a traveler in New York chooses between JFK, LaGuardia and Newark, and the useful question is what the city costs, not what one airport costs. The metro code searches all of them at once. The same is true of London on the destination side, where LON covers Heathrow and Gatwick. Where a single airport matters, the site's airport pages price it separately.

Why does the site rank cities by median rather than by this file's minimums?

A city's cheapest fare in this file is a fact about one gateway on one day. Its median across every gateway is a fact about the city. The site publishes a ranking only for cities priced from at least 15 of the 26 gateways, and ranks them on that median, which is why the ranking does not move when one airport has a good day. You can reproduce it from this file in a few lines.

What time of year do these fares describe?

The six months after the observation date, which for the current snapshot runs from early fall into late winter. These are off-season fares. Do not apply them to summer, when transatlantic economy fares run far higher, and do not compare a figure from this file with one from a different snapshot without noting that the windows differ.