Will Britons end up stranded in Frankfurt? Will UK shops run out of Swiss cheese and French wine?
The possibility of Britain breaking off from its main trading partner without any arrangements in place grew after parliament's thumping rejection Tuesday of the Prime Minister Theresa May's Brexit deal.
EU officials warned that the dreaded prospects of a "no-deal Brexit" kicking in when 2300 GMT strikes on March 29 had risen "significantly".
But what actually happens when a 46-year relationship that generations have grown to accept suddenly ends without safety arrangements in place?
Here are some things London is telling its citizens to brace for right away.
Rip-off roaming
Phone addicts could be out of luck.
Free roaming would no longer apply and UK mobile phone operators can start charging extra for subscribers who pop off to "the continent".
British officials insist that 90 percent of UK and EU carriers have promised not to quickly raise rates.
But there is no guarantee against charges going up in the months to come.
London is also urging people in Northern Ireland to watch out for "inadvertent roaming" when straying too close to the EU border with Ireland.
Frankfurt frustrations
Huge European airports such as Frankfurt can be a nightmare at the best of times.
But planes getting grounded because of lost licences would create chaos that ripples across the world.
London and Brussels have made contingency plans allowing UK carriers to continue flying to EU countries even if a deal is never approved.
But these are bare-bones arrangements that do not allow British airlines to conduct intra-EU flights.
And even these are due to expire after just six months. This means that Britons who book their Christmas vacations early might want to exercise caution this time around.
Forms, forms, forms
Britons could need to start signing their name. A lot.
Thousands of companies in Britain that do business with Europe would have to fill out reams of customs and duties declarations.
British tourists to the EU who want to rent a car may need to get international driving permits because their UK licences become invalid.
And even pets might need to jump through new administrative hoops that require them to have new passports.
People might want to check theirs as well. Those that expire within six months of travel will need to be renewed in advance.
Drug dilemma
Things turn more serious for those who rely on prescription drugs.
Two-thirds of the medicines used in Britain are imported from the EU.
Officials have urged pharmaceutical companies to create a six-week "buffer stock" on top of the three months they already have in place.
This should help cover any short-term disruptions at the border. Britain will also waive the need for EU firms to re-test their drugs under new rules.
Shoppers beware
That one-click purchase at an online store might start looking slightly less tempting post-Brexit.
The British government says "increased costs and slower processing times" for payments made in euros are a possibility.
Parcel deliveries could also get more expensive because waivers for certain import and sales taxes would expire.
Flicks and tunes
Catching up on the latest Netflix releases while coasting on a high-speed Eurostar train may become harder.
Britons could theoretically lose access to streaming services while abroad -- everything from Spotify to Amazon Prime because the UK would no longer be in Europe's "digital single market".
And the Eurostar service itself might be in trouble because old licences of UK train operators in Europe will be invalid.
Pies
Britons are proud of their Stilton cheese and Scotch whisky.
But the status of everything from Cornish pasties to Melton Mowbray pork pies will be up in the air because they will lose their "geographical indication" status in Europe.
Britain's 86 GI-protected products make up a quarter of all its food and drink exports.
Other surprises
A host of other industries and products could also be affected.
Imported sperm donations could face delays or stoppages.
Caviar supplies might start running out because Britain will not be able to trade in goods covered by European endangered species rules.
Also facing possible disruption: breeders of pedigree British horses and sheep.
