Cheap flights from St. Louis to London from $340

The month of April is, on average, the cheapest month to fly to London Heathrow Airport from St. Louis, with most prices found around $802. If you’re not able to fly to London Heathrow Airport in April, then March is your next best option. Flight prices from St. Louis to London Heathrow Airport during March average around $828.

Our data shows that Thursday is the least expensive day to fly to London Heathrow Airport. Tickets to fly out on this day can be as low as $805. The most expensive day to fly to London Heathrow Airport is Friday, with ticket prices averaging around $1,262.

Fly from Lambert-St Louis to London Heathrow for the best Lambert-St Louis - London Heathrow flight prices

You are more likely to see cheaper flights to London Heathrow Airport from St. Louis when booking weeks ahead of your departure date. In general, you can expect to find flights to London Heathrow Airport for around $1,052 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to London Heathrow Airport from St. Louis for as low as $880 on momondo.

There are 3 cabin classes available to choose from on St. Louis to London Heathrow Airport flights. Cabin price and availability will vary by airline so perform a search above to find the right deals for you.

As of October 2026, prices for St. Louis to London Heathrow Airport flights are approximately 17% more expensive when compared to flights at the same time last year.

KLM, Air France, and Virgin Atlantic are the most popular carriers operating from Lambert-St Louis to London Heathrow

British Airways, American Airlines and United Airlines are the top three most popular airlines that fly to London Heathrow Airport from St. Louis according to our data. British Airways is the first choice among our users, with 58% of people opting to fly with this airline when traveling to London Heathrow Airport. Keep in mind that there are 8 different airlines that fly to London Heathrow Airport on a routine basis, so you have a few additional options to choose from.

Historically, on average around 18% of flights between St. Louis and London have experienced a delay on any given week. The average delay length over the past 12 months has been 114 minutes.

Generally, flights departing in the evening tend to experience fewer delays. Flights at night have, in the past, seen delays more frequently in comparison.

Monday is statistically the day of the week which experiences the fewest number of delays on this flight route. Wednesday has historically seen more delays on average compared to the rest of the week.

According to our data, British Airways have had the least number of delays on this route over the last 12 months; with about 18% of their flights experiencing any sort of delay.

Chicago (ORD) was the most common stop: 50% of momondo users choosing 1-stop flights on this route connected there.

Flights via Detroit (DTW) offer the lowest average round-trip price of $947.

Flights connecting via Toronto (YYZ) have the shortest average one-way travel time: 10h 20m.

Atlanta (ATL) has the shortest average layover time for this route: 1h 22m.