The default assumption — "Europe by train" — is correct on certain corridors and wrong on others. The variables are simple: total door-to-door time, cost, and whether the journey itself is part of the trip.
Here's the decision tree.
The 4-hour rule
Within Europe, if the train journey is under 4 hours, take the train. Always. Door-to-door it'll beat flying once you account for airport transit, security, and boarding.
4-hour-or-less corridors include: Paris-London, Paris-Amsterdam, Madrid-Seville, Florence-Rome, Munich-Salzburg, Vienna-Prague (just over 4), Barcelona-Madrid, Berlin-Hamburg.
The 6-hour question
Train trips between 4 and 6 hours are case-by-case:
Take the train if the route is scenic (Zurich-Milan, Bergen-Oslo), the cities are city-center to city-center, you can work on the train, or your luggage situation is awkward for budget airlines.
Take the flight if the train requires multiple changes, the route is uninteresting, or you're coordinating with other travelers' schedules.
Beyond 6 hours: usually fly
For most travelers, 6+ hour train trips are exhausting. The exceptions are scenic flagship routes (Bergensbanen, Glacier Express) where the train IS the trip.
Otherwise: fly. Examples — Madrid to Rome (no direct train, 14+ hours via France; flight is 2h30), London to Berlin (10+ hours by Eurostar+local; flight is 1h45), Lisbon to anywhere not in Portugal (rail connections are sparse).
The cost analysis
Train fares in Europe vary wildly. Booking 2+ weeks in advance, the prices are usually competitive with budget airlines (Eurostar Paris-London £40-£80; TGV Paris-Lyon €30-€60). Same-day they're often more expensive than flying.
Budget airlines (Ryanair, Wizz Air, EasyJet) have hidden costs: airport taxis, baggage fees, seat-selection fees. A €25 Wizz Air ticket is often €70 by the time you've added everything.
The luggage rule
Budget airlines penalize luggage punitively. If you're traveling for 10+ days with checked bags, the train usually wins on cost once you've factored that in.
Trains in continental Europe accept luggage without fees up to ridiculous limits. UK domestic and Eurostar are stricter but still better than budget airlines.
The work argument
If you can work on the trip — say, you're a digital nomad — train wins almost always. WiFi is unreliable but the desk space is real, the seats are usable as a laptop workstation, and 4 hours of train work is a productive afternoon.
Plane work is fragmented (boarding, cramped, no real desk).
The strategic move
If you have 10-14 days for a multi-city European trip, base the itinerary on train-friendly hubs:
Paris hub: reach Amsterdam, Brussels, London, Lyon, the south of France by train. Hop a flight only to reach Iberia or Italy.
Munich hub: reach Vienna, Salzburg, Switzerland by train.
Vienna hub: reach Prague, Budapest, Salzburg, Bratislava by train.
Milan hub: reach Switzerland, Florence, Rome, Venice by train.
An entire 14-day trip without a single airport is realistic from any of these hubs.
The sleeper-train question
Sleeper trains in Europe are having a renaissance — Nightjet (Vienna-Brussels, Vienna-Amsterdam, Berlin-Paris), Snälltåget (Stockholm-Hamburg-Berlin), and others. They're slower than flying but save a hotel night.
Worth it for: budget travelers, romance-of-the-train trips, anyone wanting a story.
Skip if: you sleep poorly on trains, you have a tight schedule, or you're prone to motion sickness.
For specific city-pair recommendations see our train-pair guide.