Free upgrades are mostly chance - but there's a lot you can do to maximise those chances.
To help, you need to understand what's going on behind the scenes when free upgrades are happening.
Airlines almost always oversell seats - meaning if they have 21 seats available in premium economy, they may sell 25 seats.
That's because people don't show up, others pay for last-minute upgrades - and the complex modelling generally works out about right. But sometimes, all 25 people show up, meaning - in this case - four would be bumped to business class.
Here's how to maximise your chances to be one of them:
1 Dress well
If you're in shorts, crop tops or jandals - you have more chance of reaching the moon than reaching the front of the plane. Smart casual is the dress code for most airlines.
2. Travel alone
In about 99 per cent of cases, free upgrades happen to solo travellers. That's because there's ever only a few upgrades available, and generally never sitting together.
3. Belong to the airline's loyalty scheme
Airlines are much more likely to offer upgrades to their most frequent flyers, so belonging to their loyalty scheme is going to help your chances. Airlines like Air New Zealand also offer free upgrades when you reach Silver status and above.
4. Have a calm persona
If you're the kind of person who would let off a confetti cannon when sitting down in your new comfy lie flat bed, then loudly turn around and tell your fellow passengers how you got a free upgrade - you're not going to get one. Check-in agents are looking for people who will slip in without causing a scene.
5. Check how full the flight is
The day before your flight, hop on to the airline's website and see if any economy seats are available. If the flight is already showing full, this is when upgrades are likely to be happening and there are two strategies for check-in to maximise your chances. Check-in early or late.
6. Check-in early
On some flights, the Operations Team would have already allocated several upgrades before check-in opens. That often means check-in agents will be offering these upgrades early.
7. Check-in late
This is a high-risk strategy that I wouldn't recommend, but I have seen it work. Airlines expect that a number of people on each flight simply won't turn up. Sometimes, more people fly than they expect, and this can lead to upgrades for the last few people who are checking in. Many airlines close check-in later than you expect: about 45-minutes before the flight leaves. Do not take that as gospel, each airline is different.
So, sometimes people rushing to the airport thinking they've missed their flight, and check-in 50-minutes before departure, actually end up with an upgrade - simply because economy was full.
8. Offer to fly the next day
Sometimes the entire flight is full and airlines will ask if you are willing to travel the next day. They'll generally put you in a hotel, pay for your food, and if you're lucky, you'll get an upgrade on tomorrow's flight.
9. Let it slip
If you're on a honeymoon or celebrating something significant, let the crew and check-in agent know. You're unlikely to be upgraded, but could be offered Champagne before take-off.
10. Check your seat
After you've sat down, check your seat is working. A gift from the upgrade God can sometimes be a broken in-flight entertainment unit. If that's the case, tell the crew your seat is broken and politely ask if you can move. If economy is full, they may be able to slip you into a premium seat.
I had this happen on an Emirates flight once, while I couldn't move seats because the flight was full, I was told I could pick anything out of the Duty Free catalogue.
What not to do:
Don't ask for a free upgrade, don't be rude, don't try and bribe crew or check-in agents, and don't just go and sit in a spare Business Class seat. This does happen, but never for long, because the crew have a list of allocated seats.
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