IN BRIEF | Thai Airways is changing the plane it uses on its Sydney-Bangkok flights, with a larger Boeing 747-400 replacing the current Airbus A340-600.

According to Sydney Airport, the changes will come into place from 16 January 2012 and will run to at least 24 March, which is about as far forward as most airline schedules are looking at the moment.

It's slightly mixed news for business travellers: the A340 is renowned for its quiet cabin, while the 747 is prized by many business class passengers for its small, exclusive upper deck seating area.

The 747 will be slightly better for business class availability, since it has more business seats than the A340.

But if you're travelling on Thai from mid-January onwards, you should check that your seating preferences have been set properly: when planes change, your seat might not have changed properly with it.

Thai has three different seat maps and internal configurations for its 747 fleet. That makes it hard to know which type of business class seat will be on board your flight.

We'll delve more into the best seats to pick if you're travelling in business class on Thai's three separate 747-400 configurations tomorrow.