Adding a second destination to your journey normally entails paying more for your ticket. However, some airlines offer long breaks or “stopovers” at no extra charge or at a very low cost.

One of the best ways I’ve found to add places to my journeys without spending a lot of money is to use stopovers. This is a great way to broaden your travel options if you’re planning a vacation to Europe or Asia.
These airlines provide you the option to do it.
The best way to add a second destination in Europe
You can add a stop in Madrid for up to six days with Iberia Lineas Aereas at no extra cost. For instance, if you book a flight with the airline to France or Italy, you can ask for a one- to six-day stopover in Madrid.
TAP Air Portugal: Doesn’t charge you extra to add a stop in Porto or Lisbon for up to ten days.
Icelandair: Permits you to include a stop in Iceland for up to seven days.
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You can add a stop in Ireland for up to seven days with Aer Lingus at no extra cost. You must conduct your transaction using a multi-city search in which Dublin is included as a stop.
Finnair: Enables you to extend your stop in Helsinki by 24 hours for a maximum of five days. You must conduct your transaction through a multi-city search in which Helsinki is included as a stop.
Virgin Atlantic Airways: Doesn’t charge extra fees to add a 24-hour stop to a seven-day itinerary in London, United Kingdom.

Turkish Airlines: Some options offer a free hotel stay, and you can add a one- to three-day layover in Istanbul, Turkey.
How can I add stops in Asia?
The world’s top airline is Qatar Airways. For as little as $14, you may add a one- to four-day stopover in Qatar. (includes hotel).
Emirates: You may add a one- to five-day stop in Dubai for a fee that starts at $10.
You can add a stopover of one to four days in Abu Dhabi with Etihad Airways. (and book discounted hotels).
With Singapore Airlines, you may add a one- to seven-day stop in Singapore (hotel included; prices start at $41).

You can add a second destination in Tokyo while flying with ANA (All Nippon Airways). You must conduct your transaction using a multi-city search in which Tokyo is included as a stop.
You can add a one- to three-day stop in Tokyo or Osaka with Japan Airlines.
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You can add a stop in Taipei for one to seven days with EVA Air.
Stopovers are one of the best tactics for traveling and saving a lot of money.