If you're confused by the difference between a "lie flat" seat and a "fully flat" bed, you've good reason: many airlines boast about their lie-flat business class, but don't mention that it's actually on an angle. 

You hear "lie-flat bed" and have the logical expectation of a seat which converts into a bed and lets you lie flat, so you can stretch out for a sound sleep on an overnight leg.

Not so: while a lie-flat seat might extend to be flat rather than just reclined, it won't be parallel to the floor.

Instead of a true 180 degrees, they're positioned somewhere between 150 and 170 degrees, as shown below. The seat is flat, and you can lie down in it, but you'll be lying at an angle.

A fully-flat bed reclines all the way down so that it's horizontal rather than angled. That's the difference, and it looks subtle enough to let many airlines indulge in the lie-flat lie.

To confuse matters, some airlines have different seats on the same route.

Fly from Sydney to Hong Kong on a Qantas Airbus A380 and you'll find the 180-degree fully flat beds, but a Qantas Boeing 747 on the same route has angled lie-flat beds. To make things worse, both Qantas products are called Skybeds –- but only the A380's second-generation Skybed is a fully-flat seat.

Similarly, Emirates' flagship A380 has fully flat beds with aisle access for everyone, but its Boeing 777-300ER planes have angled beds at a 2-3-2 layout that's much less convenient and comfortable.

Here's a basic guide to which airlines and flights actually provide a flat bed:

The fully flat bed

For flights when you want to get some sleep, a fully flat bed in business class is a real bonus. It won't feel like home -- unless you do actually live in a plane -- but there's something about being properly horizontal that really makes sleep restful.

The most common arrangement for these seat is to have the backrest slide backwards and down, and a legrest come up and out, so you're sleeping on the seat cushion.

However, some fully flat beds fold forwards so you're actually sleeping on the padded back of the seat: Virgin Atlantic and Air New Zealand have these beds. (See the photos below for a better idea of how this works.)

As a general rule, fold-forward seats are great for a really long flight where you want to get some sleep, but sliding backwards is better for daytime flights or if you only want to nap.

On flights from Australia, the airlines with flat-bed seats in business class are:

• Air New Zealand (Business Premier on Boeing 747 and 777 aircraft)
• British Airways (Club World on Boeing 747 and 777 planes via Singapore and Bangkok)
• Cathay Pacific (both new herringbone-layout business class and the older "cubicle" pods) 
• Delta (to Los Angeles on Boeing 777s)
• Emirates (to Sydney and Auckland on the Airbus A380 only, not 777 flights)
• Etihad (to Abu Dhabi)
• Qantas (second-generation Skybed on the Airbus A380)
• Qatar (to Doha)
• Singapore Airlines (on A380 and some Boeing 777 flights)
• United (to Los Angeles and San Francisco on Boeing 747s)
• Virgin Atlantic (to London via Hong Kong)
• Virgin Australia (to Los Angeles and Abu Dhabi) 

The angled lie-flat seat

The alternative to the fully-flat business class bed is the lie-flat or "angled-flat" bed.

The angle is irritating if you're trying to get some sleep, particularly if you're wearing suit trousers, a skirt or any sort of smooth fabric. You'll end up sliding to the bottom and inching yourself up the seat all night.

However, they are sometimes better for daytime flights where you only want to nap or relax. That's especially true in comparison with the fold-forwards beds seen on Virgin Atlantic and Air New Zealand, where the sitting part of the seat doesn't have as many position options as the recline-to-flat beds on British Airways or Qantas' second generation Skybed.

You'll find lie-flat seats on Qantas' Boeing 747 and Airbus A330 long-distance flights, on Emirates' non-A380 planes serving Australia, on all Malaysia Airlines aircraft, and widely across routes other than the ones listed above as having fully flat beds.

The recliner

Reclining seats have thankfully been relegated to short hops on most airlines, although you may see them on longer regional routes that don't have a large amount of business traffic or where the flights aren't long enough to justify a proper bed.

There's not really much to say about these: they recline, and sometimes they have a footrest if you're exceptionally lucky.

Since recliners tend to be older models or on second-tier planes (the ones that used to be state of the art but are now on the less lucrative routes), they're also less likely to have decent in-flight entertainment or at-seat power.

Qantas' domestic fleet is a good example, as are most of Air New Zealand's trans-Tasman 767 flights. Just about any USA-based airline's domestic first class will be a recliner style. Singapore Airlines' regional flights from Singapore to Malaysia, Indonesia, Thailand, and even Hong Kong often have recliners too.

Ready for more in-depth info on the best kind of business class seats?

• Check out the AusBT photo guide to the different types of business class seating and cabin layouts
• See for yourself whether bulkhead seats really do give you extra legroom
• Don't miss how your personal legroom and what the airlines call "seat pitch" differ
• Pick up some tips on what to wear in the air: both the classic version and the "business casual" edition
• Boost your TQ (travel intelligence) with our five favourite advanced travel hacks