WHY should it be essential to declare a Mayday and land as soon as possible when one of the pilots becomes ill or incapacitated?
A golden rule of commercial aviation is "expect the unexpected". Supposing something were to go wrong with the aircraft an hour later? Could the remaining pilot then cope alone?
Getting a stand-in to read the pre-landing checklists is vital. The introduction of checklists is one of the biggest single contributions to air safety.
The pre-landing checklist guides the pilots through the essential tasks.
One of the first tasks is to locate the airport and to line up on the runway using the instrument landing system. The speed is checked, as is the rate of descent. The checklist also cautions the pilot to set the flaps.
These are wing extensions which enable the aircraft to slow for landing. The checklist also reminds them to make sure the wheels are down.
In the pre-checklist era an alarming number of crashes were caused by omitting these two essential checks.