I booked an airline 'stopover' deal and got a free hotel. This is why it's one of the best air travel hacks.

• I experienced Turkish Airlines' "stopover" deal in Istanbul, which included a free five-star hotel.
• It's one of the industry's best travel hacks, so long as you understand the rules.
• Some airlines stop short of complimentary stays but offer discounts on hotels and tours.

Your layover doesn't have to mean sleeping on the airport floor or surviving on a $10 hot dog.

Some airlines offer "stopover" programs that let travelers turn a layover into a mini‑vacation, giving you a few days to explore the stopover city before continuing to your final destination.

Flight prices usually stay the same, and hotels or activities may be free or heavily discounted. Think of it as two trips for the price of one — and a chance to see a new city along the way.

It might seem counterintuitive — after all, airlines are offering free perks — but the strategy boosts tourism for the home country and encourages travelers to choose a one-stop itinerary over a nonstop flight, which can ultimately be more profitable for the carrier.

I recently took advantage of Turkish Airlines' stopover deal, spending three days in Istanbul before flying to my final destination, Croatia.

It gave me just the right amount of time to shake off jet lag after the long flight from New York and check off Istanbul's main sites, like the Sultan Ahmed Mosque (Blue Mosque) and the Spice Bazaar.

Turkish is one of roughly two dozen global carriers with a stopover setup. Other examples include Copa Airlines in Panama City, Qatar Airways in Doha, Icelandair in Reykjavik, Fiji Airways in Nadi, and Iberia in Madrid.

With so many options, stopovers are one of the industry's best travel hacks — though they require careful planning and the rules vary.

You have to apply for your accommodation

For Turkish, the stopover deal includes a free hotel on either the outbound or return flight, provided the layover is at least 20 hours but no more than 7 days. This duration requirement varies from airline to airline.

The hotel reservation wasn't automatic upon booking. Travelers must separately apply for the voucher on Turkish's stopover page or via email at least 72 hours before their trip.

You can usually select your preferred hotel, but the final assignment depends on availability and isn't guaranteed.

Because part of my itinerary was in business class and my origin was the US, I received three free nights at a five-star hotel; eligible economy fares include two nights at a four-star hotel.

I stayed at the Fairmont Quasar, about 40 minutes from the airport and 30 minutes from Istanbul's tourist-friendly Old City. The complimentary room would normally run around $200 per night during the offseason.

It was a bit far from the main sites, as was the case with most of the other hotel options. Still, my room was comfortable, overlooked the Bosphorus Strait, and included breakfast.

Visa fees and transport costs between the airport, city, and hotel were not included; my cabs cost between $20 and $50, with higher fares during rush hour. There is also cheaper public transportation.

I received three nights because the program offers extended hotel stays to travelers flying from select countries, like the US, South Korea, Australia, and Canada. Those on shorter flights or from other locations receive one or two nights' free, depending on the fare class.

I slept through much of my first day as I adjusted to the eight-hour time difference, but later headed out to explore Istanbul's historic landmarks and eat a proper kebab.

The stopover gave me a buffer between the red-eye flight to Turkey and the hiking-focused trip I had planned in Croatia. The whole journey felt like less of a slog.

Not all stopover deals are alike

Each stopover deal works a little differently when it comes to eligibility rules and perks.

Typically, your layover must fall within the program's specified timeframe, and your itinerary must be on a qualifying route. There may also be restrictions on fare class.

Most airlines also require you to add the stopover through a dedicated portal or customer service, either at the time of booking or within a set window afterward.

Like Turkish, a few sweeten the deal with complimentary stays. UAE's Etihad Airways includes up to two free hotel nights in Abu Dhabi as part of its program.

Ethiopian Airlines provides a free night at its Skylight In-Terminal Hotel at Addis Ababa Airport for layovers between eight and 24 hours. That's enough time to sleep, but little chance to explore the city.

Others lean on discounted options. Qatar Airways, for example, offers name-brand hotel rooms in Doha at a small fee, ranging from $14 per person for one night to $76 per person for four nights.

Airlines like Copa and TAP Air Portugal offer structured stopover perks, such as discounts on hotels, restaurants, and experiences. Emirates also includes a stopover, and travelers can optionally add a curated multi-day tour in Dubai for an extra fee.

Others, like Air Canada, Air France, and Dutch carrier KLM, simply let travelers turn a layover into a multi-day visit without risking a fare hike, making their stopovers more of a routing perk than a bundle of freebies.

That means travelers are largely on their own for planning hotels and activities. Even so, stopovers remain a smart way to see a city you might not otherwise make time for.

For aviation and travel aficionados like me, they're a double win: a chance to experience different airlines and aircraft while squeezing more cities into a single trip.