Playing devils advocate :
You can insure yourself against whatever risks you feel appropriate and it is probably very wise to do so. If your employer pays the premiums for you for any of these risks then the revenue are likely to treat these payments as a benefit in kind. Tax will either be payable on the premiums for providing the insurance policy or alternatively on the receipt of the benefits themselves.
Officedesk consider these responses to your arguements which are likely to be the revenues response.
1) Many individuals can lose their income for a variety of reasons including the ones you suggest. They may be able to take out insurance to protect themselves from the full effects of such loss but that would be discretionary and not subject to tax relief. The amount of tax you pay is porportionate to your earnings and irrelevant to your speculative state of health in later life. This applies to the rest of the population and ought therefore to apply to pilots who are no different in this regard whatever the perceived level of risk may be.
2) Tax is payable on earnings and any benefits in kind are assessed as additional earnings for which a tax charge is also payable. It is very interesting how much your career has cost but totally irrelevant to the revenue for the purpose of this consideration. Many other professions are of equal, greater or lesser difficulty but are not subject to relief for insurance policies of this kind. There is no link between the cost of your training, the VAT you have paid and any relief for discretionary insurance policies.
3) There is always a threat of hardship if any working person loses their income and insurance policies to protect against that risk may be available to the individual, but they are not exempt from tax.
You are right it may be very advisable to take out this type of insurance for all the reasons you suggest. It is also very wise to take out home insurance and car insurance and life insurance. However with the exception of third party liability car insurance ( which is usually compulsory for car drivers and not tax exempt either) non of these are anything other than discretionary policies. If you are in the fortunate position of having your employer pay your premiums for any of these then you must pay the tax at the approriate rate for the benefit in kind. Given your compelling arguements for how vital this insurance is you would no doubt agree that the tax is indeed a very small price to pay for the benefit that has been provided and paid for by your employer. If the employer did not provide this benefit then you would no doubt seek to provide this benefit at your own cost which would presumably be two to three times as muchdepending on your marginal tax rate.