Flights JQ747/JQ748 are to/from Launceston Airport , which does not have aerobridges : Facilities at Launceston airport do not include aerobridges to board or disembark aircraft.
All access onto the aircraft is via aircraft stairs or mechanical lifting equipment (Personal Assistance Device) operated by the airlines.
I would strongly advise you to contact the airline and notify them that you will likely need assistance, and arrive early for check in so you can ensure they're ready.
On the Sydney side, Jetstar flights typically do use aerobridges, but these are some bus-only gates as well.
The airline will be able to advise you regarding this as well.
As for a generic way to find out, I suppose you could always look at the airport in the satellite view on Google Maps , but even if the airport has gates does not guarantee that your flight will use them.
So, again, contacting the airline is by far your best bet.
travel.stackexchange.com/users/1893/lambshaanxy
There is no way to guarantee either.
Aircraft parking assignments are planned in advance, but subject to change without prior notice due to various reasons, such as the previous flight using the gate being delayed.
You can decrease the risk of a bus gate (stairs) by choosing flights that come and go during the daytime, early evening, as they do their best to park turn around flights at the gate for more efficient loading and unloading.
Flights that arrive late or depart very early may use aircraft that park overnight, which would be more likely to use a bus gate to keep jet bridges open for turn arounds.
But if the flight uses a bus gate or stairs, then all airlines and airports have means to board passengers with mobility issues, ranging from simply carrying a specially designed wheelchair up the stairs, to using a lift truck to move the passenger and wheelchair up to one of the service doors.
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It is not the flight/plane themselves that could be the problem, but the airport.
If your friend's family member needs extra help to board the plane, then they should ask the airport/airline directly for assistance.
(As soon as possible) For example, I assume they will go to Launceston airport in Tasmania.
They have a "disability/accessibility plan" that supports different disability (wheelchairs and other ) https://www.launcestonairport.com.au/accessibility
I assume Sydney Airport has the same kind of assistance.
Either jet-bridges if boarding from the airport, or ramps (or elevators)
if boarding from the tarmac.
travel.stackexchange.com/users/8279/Max
As far as I am aware there is no generic way to discover this information.
See the discussion at Ryanair
Using Jetbridges, Where? about this topic where a Ryanair crewmember was unsure whether they use it at BUD or not as it was not his/her route and also someone pointed out sometimes it's just "depends" and that easyJet some places uses both .
travel.stackexchange.com/users/4188/chx
Trying to address your need rather than answer your question directly: Visit the airport's website.
Figure out the best telephone number to call regarding service for passengers with disabilities/
special needs (it might just be some single center service number of course).
Call and tell them about your friend's physical trouble, and ask them how can it be arranged for him not to be inconvenienced/suffer any pain.
Suggest options such as: Ensuring an air-bridge; offering to take him out via an elevator down to the tarmac, then using a mobile lifter to the airplane's entrance; or whatever arrangement they suggest that I might not have though of (ramps?
being carried on a chair?).
I'd say that's the best you can do in your situation.
travel.stackexchange.com/users/33321/einpoklum
If the airport is small it may not have bridges and thus you know it will be stairs.
Otherwise you can't know as it can be situational:
"They don't have a gate for us, we are going to use stairs."
It's happened to me twice at major (admittedly foreign) airports.
And since I wrote this I've had to use stairs twice at major US airports.
Seattle has some "gates" that are always actually stairs.
travel.stackexchange.com/users/1764/Loren Pechtel
A colleague has a family member who struggles with the stairs, and wouldn't be able to climb (injury).   They've spotted a trip to Tasmania on Jetstar from Sydney, but are wondering if the planes have stairs or an  air-bridge/jet-bridge .  The flights are JQ747 and JQ748, but I'd prefer a more generic way of finding out this information?
How to tell if your flight has an air-bridge or stairs?
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<air-travel><airports><accessibility><airport-terminals>
travel.stackexchange.com/questions/83496
travel.stackexchange.com/users/101/Mark Mayo
There is no generic way of finding out in airports where both are used, and the airport can change gates without prior notice. Launceston Airport does not have aerobridges and Sydney has both aerobridges and bus-only gates, but all airports will have ways of accommodating disabled persons, and you can contact them ahead of time to notify them. It is genrally not possible to know how your flight will be boarded in advance, i.e., using an aerobridge or stairs. If a passenger has moblity issues, it is recommended thy contact the ailrine which will provide boarding assistance in any case.
There is no generic way to know if a flight will be boarded via aerobridge or stairs. Small airports may not have aerobridges and large airports may board some flights via stairs. It is best to contact the airline if you have a mobility problem and they will arrange to provide assistance wtahtever the method of boarding.