You may access a lounge (first-class, where available, if in First Class) if all of the following conditions are met:

1. You are travelling on a oneworld-marketed and -operated flight [1]
2. You are travelling in or connecting to/from First or Business Class [4]
3. You are travelling from the airport (i.e. origin or transit; not arriving at your final destination [2])
4. You enter the lounge before 06:00 after the day of travel [5]

subject to certain lounge exclusions identified on the oneworld website (see https://www.oneworld.com/airport-lounges ), e.g. "Light" Business fares, super-premium AA/BA lounges.

You may access a lounge (first-class, where available, if you are Emerald) if all of the following conditions are met:

1. You are travelling on a oneworld-marketed and -operated flight (even if you are travelling Economy, even "Basic" Economy fares)
2. You are oneworld Sapphire or Emerald
3. You are travelling from the airport (i.e. origin or transit; not arriving at your final destination [2])
4. You enter the lounge before 06:00 after the day of travel [5]

subject to certain lounge exclusions identified on the oneworld website (see https://www.oneworld.com/airport-lounges ), e.g. AA/AS/QF paid membership, AA/AS elites and domestic travel, UL elites and regional flights, super-premium AA/BA/QR lounges.

You may bring one guest into the lounge if all of the following conditions are met:

1. You may access the lounge (whether first-class or business)
2. The guest is travelling on a oneworld-marketed and -operated flight (does not have to be the same flight as you)
3. The guest is travelling from the airport (i.e. origin or transit; not arriving at their final destination [3])

Note: the rules are different for oneworld connect (see https://www.oneworld.com/members/fiji-airways for the only current such airline).

[1] The rules at https://www.oneworld.com/airport-lounges for direct flights just say "fly First Class or Business Class with any oneworld member airline" but it is safer to assume this means both marketed and operated by a oneworld airline.

[2] The rules at https://www.oneworld.com/airport-lounges say "at the airport from which the oneworld flight on which the eligible customer is travelling departs". There are situations in which you can access a lounge on arrival, e.g. when flying AA domestic (see https://www.aa.com/i18n/travel-info/...lub-access.jsp ), but this is airline-specific, not a oneworld benefit.

[3] The rules at https://www.oneworld.com/airport-lounges for direct flights just say "The guest must also be travelling on a flight operated and marketed by a oneworld carrier[/airline]" but it is unlikely this would be accepted as covering arrival at final destination, and in any case it is generally impossible to access departure lounges on arrival (see also [2]).

[4] If your flight is not direct and you have an international segment with > 5 h flight time, the rules at https://www.oneworld.com/airport-lounges are that this is the one in which you have to be travelling First or Business, which then applies to all segments. The rules are not clear if you have two such segments and one is Economy, or if you don't have any such segments, but it's likely the rules would be applied for each segment independently.

[5] I don't know what this is about!