United Airlines has attracted a lot of criticism for denying boarding to 3 young female passengers dressed in leggings, a staple wardrobe item for girls/women of all ages. Apparently they were travelling on discounted tickets as relatives of UA employees and one of the adults was wearing shorts. When using such tickets, UA expects passengers to dress appropriately as they are considered to be representatives of the airline whilst enjoying this "perk".
Holiday airlines such as Thomson and Thomas Cook are more relaxed in terms of dress than ones such as Virgin Atlantic where there may be a mix of business and leisure passengers. What they usually say is do not wear anything with offensive/ obscene slogans or logos.
Guys, whether your body remains a temple or is in ruins, it may be okay to walk around the pool or beach wearing a vest/singlet or unbuttoned shirt (I mean all buttons), but at the airport or onboard the flight it's not very respectful to your fellow passengers or staff. Ladies, if you've lost the battle to retain a youthful figure, wear something suitable that fits instead of lycra crops that are two sizes too small.
Seriously, until pictures are posted of the offending leggings, we will not know if the airline staff were being pedantic or genuinely considered they did not meet their standards. This was a flight within the USA but how many passengers actually consider the law and culture of their destination when deciding what to wear either on the flight or in the resort.