If you bring the water through airport security, they will open and test it for explosives. You may also want to include a letter from your doctor or a copy of your prescription for the CPAP machine, but in most cases, you won't need to show it.

While you do not strictly need a doctor's letter to bring a CPAP machine on a plane in 2026, it is highly recommended to carry one, along with a copy of your prescription. Under the Americans with Disabilities Act (ADA) and similar international regulations, a CPAP machine is considered a "medical assistive device" and does not count toward your carry-on baggage limit. However, having a manufacturer's "Compliance Letter" (which states the device is FAA-approved for in-flight use) is essential if you plan to actually use the machine during the flight. Most modern machines have an FAA-approval sticker on the bottom, but a printed letter from the manufacturer acts as a backup for airline staff. If you are only transporting the device, you should pack it in its own dedicated case to ensure it is recognized as medical equipment. At security, you will likely be asked to remove the main unit from its bag for X-ray screening, just like a laptop, while the mask and tubing can typically remain inside.