Flights to the UK or via international airports including London Heathrow, Gatwick, Manchester and Birmingham are likely to be thrown into chaos Wednesday evening through Thursday evening: UK Border Agency (UKBA) customs and passport control staff will join a widespread public sector strike.
It'll be a particularly severe problem for connecting Qantas passengers, who use the British Airways Heathrow hub to connect to most European flights.
An official UK government statement reads: "People travelling into the UK may experience delays at border control. The impact of the strike will be different at individual ports, airports and international rail terminals. We have put contingency plans in place and will work hard to keep delays to a minimum."
UKBA has also written to airlines suggesting that passengers should avoid flying on Thursday if possible, according to a report in British newspaper The Guardian.
Airlines are expecting that "passengers may experience delays at the border", and that "passengers who can travel on an alternative day may therefore wish to do so", UKBA has told airlines.
Passport checks and customs screening, already an involved process with lengthy queues for non-UK/European Union passport holders, are likely to be among the worst affected.
What should you do?
If you have a connecting flight through Heathrow to other European airports, consider rerouting your flight through another country.
Qantas flies to Frankfurt via Singapore, Virgin Australia's codeshare partner Etihad has a number of European destinations, and other carriers have alternative options in Europe and elsewhere.
If you do connect through Heathrow, make sure you know what connecting flights are available, and whether you'll be stuck for 24 hours if you miss your connecting flight.
And don't forget our advice for being prepared when you know a flight delay or airport disruption is possible.
We'll continue to bring you the latest at Australian Business Traveller, both here at www.ausbt.com.au and on Twitter: @AusBT.