There is not, to my knowledge, any requirement to have or hold a 1st Aid Certificate (by CASA); although some employers may have it as a prerequisite.
HOWEVER!!
EJECTOR, I don't know where you get this
but non (sic) of them will help any way as they can get sued. They are not even allowed to give out Panadole (sic) now, incase the moron sues them
BOLLOCKS!!
Common law enables anyone to sue anyone for just about anything; BUT under the same law there is a protection (no, NOT a 'Good Samaritan Act') that "a person acting in good faith, within the bounds of their training and / or knowledge (however vast or limited) may not be held liable for acts taken in that vein which would be viewed as reasonable by a person of similar background or training". (or words to that effect). ie, if you act in good faith within the bounds of your 1st Aid or whatever training, no suit against you will be upheld.
Trust me on this, 1st Aid training CANNOT get you sued, but MOST CERTAINLY CAN HELP YOU SAVE LIFE AND / OR LIMB. Do yourself a favour; if you are contemplating a career that puts you in daily contact with people who will regard you (being uniformed) as a source of leadership, knowledge and authority (such as a Commercial Pilot) AND are often less than super fit / healthy; you NEED decent 1st Aid training.
DO 'Worry about it'