After extensive research, we can exclusively reveal that getting flight upgrades is a simple matter of mathematics, as shown in the equation above.
The aim is to spruce up your Passenger Name Record (PNR) with a bit of creative Other Significant Information (OSI), ideally alongside a note confirming susceptibility to Deep Vein Thrombosis (DVT), written by a Friendly General Practitioner (FGP). With all this in the bag, getting a Suitable For Upgrade (SFU) stamp on your boarding pass should be a piece of cake.
The key is the point of first contact. When booking your flight at a travel agent, act all Billy Business: "I'm quite the jetsetter you know. I believe I once shared a bottle of fizz with your MD over Sri Lankan airspace." Then the sob story: "Frightfully tricky this DVT business, I managed to pick up a bout of the stuff on an overnight from Shanghai recently. Here's my doctor's note." Once lulled, the agent will make a note of your status and maladies in the OSI section of the booking. This will pop up on your PNR behind the check-in desk at the airport, and - kazam! - upgrade.
We also managed to track down a former air hostess who spent several years working for a major British carrier that may or may not be British Airways. With her insider info we have included a fallback option within the equation. Like me and you, flight staff are real people with real needs such as Mint Imperials and glossy mags. Upon entering the airport, our source would often visit certain retailers to stock up on provisions before the big flight. Said ex-air hostess exclusively revealed to the Guardian that, having chatted to a stranger during a WH Smith Rendezvous (WHSR), she had recommended him for an in-flight upgrade when he happened to be on her plane.
If our equation somehow fails, here are some other methods you may wish to use:
The suck-up
Pick an airline and stick to it. Enrol in their Frequent Flyer Programme on day one. Use their recommended credit card and hotels frequently. Send Christmas cards and round robins. Once the air miles and frequent flyer points have stacked up, cash them in for an upgrade.
The career path
The most dedicated of blaggers will start planning for free upgrades right after GCSE results. A decent epithet may lead to better legroom. Titles such as Reverend, Doctor, Professor, General, Archduke (etc) are particularly hard to refuse at 20,000 feet. Abstinence is another good one - kids are a guaranteed upgrade-blocker.
The numbers game
Book yourself on to a predictably busy flight, hoping that it will be overbooked, and then turn up fashionably late, preferably in your best gear. The overbooking will force the airline's hand: either they put you in first class there and then, or put you on a later flight with an upgrade for the inconvenience.
The gate shmooze
The airline agents at the boarding gate have more upgrading authority than any other employee. Having arrived at your gate early, approach carefully with open palms, and have a quiet word with the agent well out of earshot of any other passengers. Ask if there are any "aisle seats by the window" available.
The recent accident
Purchase newspaper, wallpaper adhesive and matted textile from shop. Fashion papier-mache cast and apply to limb. Supplement with crutches if necessary. Make a continuous fuss upon entering airport until boarding plane, accentuating pained moans when in vicinity of airline staff.
The high brow
Pay the full price on a ticket. Chances of an upgrade are slim to none if you've bought your tickets on the cheap 10 minutes ago from cheekychappie.com. If, however, you clearly indicate at check-in that you are a discerning full-pricer, the staff might take pity, and upgrade you from the riff-raff.
The visual tool
If you ever make it into the hallowed aisles of business or first, guard your stickers with your life. Any attached indication on any luggage that you have previously flown first class may tip the golden scales in your favour. Thrust under check-in staff's nose.
The old favourite
Unfortunately check-in staff have become increasingly savvy to the honeymoon shuffle, so beat the competition by bringing documentation. A stamped wedding certificate will do. If you're willing to go the extra mile, turn up in full marital outfit with clearly labelled old, new, borrowed and blue items.