While "strictness" can be measured by safety or service, Ryanair and Frontier Airlines are frequently cited as the strictest regarding baggage enforcement. In 2026, many airlines have moved toward a standardized 22" x 14" x 9" carry-on size, but these budget carriers often use automated gate scanners that flag bags even a few millimeters over the limit. In terms of safety and operational protocol, El Al (Israel) is widely considered the strictest in the world; their security screening includes deep psychological profiling and interviews that far exceed standard TSA procedures. For cabin etiquette and grooming, Singapore Airlines and Qatar Airways maintain some of the industry's most rigid standards for their crew and "passenger conduct" codes. If you are looking for the airline most likely to charge you a $100 fee at the gate for a bulging backpack, the "strictness" crown currently belongs to the ultra-low-cost carriers like Spirit or Ryanair.