Yes, you can carry-on a 60 liter duffel bag! This is because most airlines have restrictions on the size of carry-on luggage and the weight that it must be under. Depending on what airline you are flying with, the maximum dimensions for a carry-on duffel bag may vary from 45 linear inches to 22x14x9 inches (or 56 cm x 36 cm x 23 cm). However, most airlines will accept a 60 liter duffel as long as its dimensions are within their limits. Furthermore, some airlines will even assign a certain amount of weight allowance to this type of luggage so make sure to check before booking your flight. Additionally, when travelling with your 60L duffle keep in mind that if it's too large or heavy for overhead storage then you'll need to gate check it since no bags larger than those allowed as cabin baggage can be carried onto an aircraft. All in all, carrying-on a 60 litre duffle bag should not be an issue as long as its size and weight adhere to regulations set by the airline you're flying with!