Pulmonary Disease and Air Travel
Healthy passengers usually tolerate air travel well, but the aircraft cabin environment can challenge those with pulmonary disease. Approximately 12% of in-flight emergencies are due to respiratory problems, which is the third most frequent cause of diversions due to medical emergencies. Persons with significantly compromising pulmonary disease require advance planning for travel, including risk assessment, basic planning measures and advice, vaccinations, and information on flying with oxygen or other medical devices.

The air pressure in an airplane cabin falls with increasing altitude, resulting in a decrease in blood oxygen level (hypoxemia), more so in elderly passengers. Hypoxemia has a wide range of effects on circulation, but the effects do not become apparent until marked hypoxemia occurs.
Hypoxemia can be life threatening. Persons experiencing symptoms in flight should seek immediate medical attention.

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ICAO Annex 17 to the Convention on International Civil Aviation (the Chicago Convention) Security Safeguarding International Civil Aviation Against Acts of Unlawful Interference (March 2011) defines a disruptive passenger as:
A passenger who fails to respect the rules of conduct at an airport or on board an aircraft or to follow the instructions of the airport staff or crew members and thereby disturbs the good order and discipline at an airport or on board the aircraft.

👮‍♂️ICAO’s levels of threat are as follows:
Level 1 — Disruptive behavior (verbal);
Level 2 — Physically abusive behavior;
Level 3 — Life-threatening behavior (or display of a weapon);
Level 4 — Attempted or actual breach of the flight crew compartment.

The flight was en-route from Washington DC to San Francisco when it was forced to make an unscheduled landing in Denver, where the passenger was freed upon landing.
United Airlines confirmed in a statement that flight 1554 was diverted to assist a passenger “who was in the lavatory when the lavatory door became inoperative.”
“The passenger was safely removed from the lavatory after landing, and customers have since continued on to their destination on a new aircraft,” the statement said.

P.S. Such situation can happen with a crew member as well. Here is the recording:

Lightning is an atmospheric discharge of electricity. A lightning strike can be very distressing to passengers and crew but damage to an aircraft in flight which is sufficient to compromise the safety of the aircraft is rare.

Effects
• Aircraft Damage. Structural damage to aircraft from lightning strikes is rare. Nevertheless, there have been many incidents of lightning strikes leaving puncture holes in the radomes and tail fins of aircraft and damage to control mechanisms and surfaces.
• Crew Incapacitation. Momentary blindness from the lightning flash, especially at night, is not uncommon.
• Interference with Avionics. A lightning strike can effect avionics systems, particularly compasses.
• Engine Shutdown. Transient airflow disturbance associated with lightning may cause engine shutdown.