For travelers flying with TUI Airways (identifiable by flight numbers starting with 'TOM' or 'BY'), there is currently no penalty or charge for failing to check in online. TUI provides free airport check-in desks where staff will print your boarding passes at no extra cost. This distinguishes TUI from "ultra-low-cost" carriers like Ryanair or Wizz Air, which can charge upwards of £55 per person for airport check-in services. However, checking in online (which opens 48 hours to 14 days before departure depending on your booking type) is still highly recommended to secure seat assignments and speed up the baggage drop process. A critical caveat exists if your TUI holiday involves a partner airline (such as easyJet, Ryanair, or various international carriers). In those instances, you are subject to the partner airline's specific policies; if you are booked on a Ryanair flight through a TUI package and fail to check in via the Ryanair app, you will likely be hit with their standard airport check-in fee. Always verify the "Operating Carrier" listed on your booking confirmation.