What is what does it mean when a flight is operated by another airline?

When a flight is "operated by" another airline, it means that while you may have booked your ticket through one airline (the "marketing carrier"), the actual flight is flown by a different airline (the "operating carrier"). This is usually due to a codeshare agreement between the airlines.

Here's what it means for you:

• Who flies the plane: The planes, pilots, and cabin crew belong to the operating airline.
• Branding: The plane will likely have the operating airline's branding on it.
• Service standards: You'll experience the in-flight service and amenities of the operating airline, not necessarily the marketing airline.
• Check-in: You will usually check in with the operating airline, though sometimes you can check in with the marketing airline depending on the agreement.
• Frequent flyer miles: Mileage accrual depends on the specific agreement between the airlines and the fare class of your ticket. You might earn miles with either the marketing or operating airline's program, or possibly neither. Check your frequent flyer program terms for details.
• Baggage allowance: The baggage allowance is typically set by the operating airline but could depend on the agreement of two airlines.
• Potential confusion: Be aware that the flight number might be different depending on which airline you are looking at. Always confirm the operating airline when checking in or inquiring about your flight.

In short, "operated by" indicates the airline physically flying the plane, which influences your experience and potentially affects your mileage earnings.