Jetstar is a subsidiary of Qantas, which runs its own frequent flyer programme and has nothing to do with British Airways' Executive Club. Announcements made on Qantas, and on Jetstar, will be tailored to members of the QFF programme and do not describe, nor are they intended to describe, the situation for members of any other programme. It is therefore incorrect to assume that anything stated onboard about earning opportunities applies to British Airways Executive Club, or any programme other than the native programme of the airline in question (you would, presumably, have understood that the announcements on board would not apply to opportunities for, say, passengers having a Lufthansa Miles and More account, or to passengers having an Etihad Airlines account, etc). Each individual oneworld programme is free to handle its affairs separately - so nothing that was stated on board should be taken to indicate that BA Executive Club members (or any other oneworld programme member, apart from Qantas) would earn Miles/Tier Points.

The fact is, Jetstar is not a oneworld member airline, nor a oneworld affiliate. It was therefore incorrect to assume that any Jetstar flights would earn Avios and Tier Points on the basis of the oneworld alliance. Furthermore, Jetstar is not a partner airline of the BA Executive Club, so there is no mechanism, either within oneworld or outside of the alliance, for BA to give you any credit for flights taken on Jetstar. Additionally, the Jetstar website says nothing about you being able to earn miles - it merely shows you how to earn in Qantas' programme.

BA is quite clear about how Avios and Tier Points are earned on all of the oneworld airlines, and on all of its other partner airlines (Aer Lingus and Alaska Airways). As you will see from the page detailing Qantas earning in BAEC only flights operated by JetStar and booked under a QF flight number, in economy "L" class as part of a oneworld explorer fare, will earn miles.

You simply cannot claim any Avios or Tier points for your Jetstar flights from BA. If you have (or wish to open) a QFF account, you may be able to claim credits for these flights there, instead (Qantas Frequent Flyer does not give points/credits for ALL Jetstar flights - it depends on your fare class, so you may not even receive anything from Qantas, either).