I have heard that some Inspectors have allowed the cost of flying training against earnings but that most won't. Certainly, I would err on the side of caution and suggest that it isn't allowable.
However, it's not because it's capital expenditure but because professional qualifications (such as flying and accountancy) are classified as NVQ level 5 and qualifications at that level do not get tax relief.
So if you wanted to retrain as a plumber, you could get the tax relief. Thank Norman Tebbitt.
However, I hope you were reclaiming the VAT as that is allowable.
Go and see an accountant and have a chat.
Cheers
Whirls