Backwards:
If anyone hasn't run the scenarios through the pension calculator, do it now! As a mid 40s PAS Sqn Ldr on AFPS75 (soon to be 15), I can leave on my 55th birthday in 10 years or so, and get about 100k lump sum plus just over 29k /yr. If I do 5 more years I get a 69k lump sum and just over 46k /yr. 17k /yr extra for a loss of 31k lump sum is a big boost even taking into account that the lump sum is tax free and the income will be taxed at 20/40%.
I see that (20x46k)+69k is 989k so below the magic 1 million mark!
It might not apply to you specifically, but remember that if you opt for 'protection' and froze your pension pot, you have to take into account the annual CPI growth that would grow it (ho ho) - and any other post RAF pension savings. If it did drop to £1,000,000 you'd be a bit too close for comfort.