TUI Airways Flight Tracker (BY / TOM) - Plane Finder.

In the world of aviation, the "BY" IATA code belongs to TUI Airways (formerly Thomson Airways), a major British charter and leisure airline. Based at London Luton Airport, TUI Airways is part of the global TUI Group and operates a massive network of flights to vacation destinations across Europe, Africa, Asia, and North America. If you see a flight number starting with BY (e.g., BY246), it is likely a holiday flight heading to a sunny spot like Mallorca, the Canary Islands, or Orlando. Interestingly, in 2026, while the airline's parent company is German, the "BY" code remains a legacy of Britannia Airways, which was once the largest charter airline in the world before merging into the current TUI brand. This airline is a staple for UK travelers booking "package holidays," and you will frequently see their distinctive "blue and red" livery at airports like London Gatwick and Manchester.

That’s an excellent question because it gets into the specifics of airline codes.

The answer is: No current, active airline flight number starts with “BY”.

Here’s the detailed explanation:

1. The Two-Letter Code (Airline Designator)

The letters at the beginning of a flight number are the IATA airline designator code. This is a unique two-letter code assigned to each airline.

• “BY” is the IATA code for TUI Airways. This is a British charter airline, formerly known as Thomson Airways.
• Therefore, any flight operated by TUI Airways will have a flight number that starts with BY### (e.g., BY 1234).

2. The Common Misconception: “BY” as a Prefix

When people ask this, they are often thinking of the radio telephony designator, which is the name used by pilots and air traffic control. This is usually a pronounceable version of the airline’s name or call sign.

• TUI Airways’ radio telephony/callsign is “TOMSON” (a holdover from its Thomson Airways days).
• So, while the written flight number is BY1234, a pilot would say: “TOMSON one-two-three-four.”

3. Why the Confusion Exists

You might hear stories or see old references to flight numbers starting with letters. This confusion usually comes from:

• Old Documentation: Very old systems or informal contexts might have written flight numbers with prefixes like “BY” pronounced as part of the number.
• ICAO vs. IATA: The ICAO code for TUI Airways is TOM, which is three letters. In some technical operational contexts, this might be used, but not in public-facing flight numbers.
• General Aviation: Private or non-commercial flights might use registration-based call signs (like “November-123AB”) which are different from airline flight numbers.

Key Examples:

• TUI Airways Flight 123: Written as BY123, spoken as “TOMSON one-two-three.”
• Delta Flight 234: Written as DL234, spoken as “DELTA two-three-four.”
• British Airways Flight 1: Written as BA1, spoken as “SPEEDBIRD one.” (