Guidance on making complaints about your in-flight experience
The only regulations on seating relate to ensuring that passengers can sit upright in the seat and stand up and move to the aisle without undue difficulty. Airlines therefore must have a minimum spacing between seat rows (“seat pitch”). But they do not have to recline, nor are there any regulated comfort standards.
Many airlines offer the facility to pre-book a particular seat but they will not guarantee the request. Some airlines invite passengers to pay a fee to pre-book a seat. But even this is not a guarantee (though if you pay for an allocated seat and you do not get it, then you should get this fee back).
Some airlines provide free meals and refreshments. However they do not have to do so. If you did not receive a meal or it was not up to the standard you were expecting, you should not expect much more than an apology should you complain to the airline. The same is true if your preferred choice of meal is no longer available by the time the trolley reaches you; or if you have requested a special meal for dietary or religious reasons. Passengers who have medical conditions for which they must have specific foods or eat at specific times should always carry the necessary food with them.
Airlines do not have to provide in-flight entertainment, so if there was none available on your flight, or if the entertainment was not what you were expecting or working, you should not expect more than an apology and should you subsequently complain, at best you are likely to only get a modest goodwill gesture.
The air that circulates around aircraft cabins can get stuffy. But it is worth knowing that the air is passed through high efficiency filters, which remove bacteria, viruses and particulate material - and that it is filtered more regularly on a plane that in a normal air-conditioned building. There is therefore no evidence that disease and viruses can spread more easily on an aircraft. However, the air is dry since there is very little moisture in the air taken from outside the cabin to replenish supplies when the planes are at high altitude. But again there is no evidence that the dry air results in significant internal dehydration in those otherwise fit and well.
Surprising though it may seem, airlines are not required by law to provide toilets. Thankfully most do except perhaps on very small aircraft on very short routes. If one or more of the toilets on board are out of order, there are no regulations under which an airline must compensate passengers for the inconvenience.
Cabin crew are present first and foremost for safety reasons. There are no regulations against which airlines can be held accountable if their crew are rude or provide a substandard level of service. If they are inattentive, unfriendly or even rude to you, an airline might investigate a particular incident but would be unlikely to offer much in the way of compensation.