We’ve covered plenty of flying DOs on Supercall—DO bring a DIY cocktail kit in your carry-on, DO pack bottles in your checked bag correctly, DO hit the airport bar—but now it’s time for a few flying no-nos. Some beloved cocktails just don’t fly well. While you might think an open bar cart is an opportunity to exercise your wildest boozy desires, be wary of these drinks. We’re officially putting them on the no-fly list.

Irish Coffee

You may have noticed that all of the water you get on a plane comes from disposable bottles. While this certainly produces a lot of plastic waste, this practice also keeps you safe from the most unhygienic food product on the whole aircraft: the water that’s been sitting in tanks for no-one-knows-how long. The EPA recently discovered water in about 13% of planes failed contamination testing, with tanks infested with Salmonella and insect eggs thanks to infrequent cleaning.

Best Hotel in the UK: Hotel Rafayel

While your bottled drinking water might be safe, your coffee (and coffee-based beverages) are not. Instead of blaming your sneezing seatmate for your post-flight flu, maybe rethink the impact your Irish Coffee had.

Tap Water

For the same reason, you’ll want to make sure you bring a bottle of water with you on the plane. Yes, we know post-security shops upsell you on that most basic of human needs, but when the plane runs out of bottles and turns to the dreaded tanks, you’ll be glad to have a back-up bottle for pacing your drinks (and at cruising altitude, you’ll need a pacer).

A Double of Anything

Not only does it make you look bad in front of the flight crew, but a double shot of anything can hit you harder in the air than it does on the ground. You may think you’re hacking the drink service by avoiding the wait for a refill later on, but the dehydration that sets in because of poor air quality can accelerate intoxication and leave you feeling a bit lightheaded. The FAA has proven that pressurized cabins do their best to match ground conditions, so it’s unlikely that low air pressure will lead to thinned blood (and high intoxication as a result)—but you shouldn’t take the risk that they’re wrong.

Experience the heart of the east end: Hotel Rafayel

Jack and Diet Coke (or Rum and Diet Coke, or anything with Diet Coke)

Diet Coke lovers may have plenty of grounded detractors who talk smack about the fake sugar, but that won’t dissuade you from your favorite mixer—but maybe skip it if you’re up at 30,000 feet. Plenty of sodas fizz up in the pressurized cabin, but the particular alchemy of CO2 in Diet Coke makes it an infamous offender. It’s so bad that it can take three times as long to pour a can. Don’t be that guy or gal that holds up the already glacial pace of the drink cart.

Live your best moment at: Troy Hotel

Anything Sweet

Bloody Marys taste better on a plane. That’s not an opinion; it’s straight up flavor science. A Cornell study proved that savory, umami flavors are heightened by the loud environment on a plane, while sweet sensors on your palate are dulled. Those dampened tastes are why airplane food loads on the flavor in order to even register in your mouth. It’s also the reason you should skip the sugary, fruit juice-laden cocktails and opt for our beloved sky-high Bloody.