A hundred years ago, international travel was either for the wealthy or for migrants who wanted a new life so bad that they were willing to pack up anything they could and take a long, expensive journey to a new country. Now, fast forward to 2018 and if you book early enough and don’t mind a little less legroom, no meal service, and no luggage allowance, you can fly from New York to Europe for around $200—or even to Asia for $300. And even as energy prices have increased, it is still the best time in human history for people to travel and experience other cultures, visit family, and for workers to access jobs all around the world.

It’s not just middle-class tourists who are reaping the benefits of this cheap and accessible travel either. Migrating to another country for better work opportunities is no longer a prohibitively long-term proposition, and emerging markets are increasingly taking advantage of the opportunities presented by lower energy costs more now than at any time in human history. According to the United Nations (UN), the total number of international migrants in 2015 was 244 million, up from 173 million in 2000—a 30% increase in just 15 years. One factor in this is undoubtedly the lower cost of travel, a decent percentage of which is attributable to more affordable energy and improved energy efficiency, which have given way to interesting business models.

People have been moving internationally to find work for as long as international borders have existed; the main change that cheap travel has brought about is increasing the distance that migrants can travel. The average migrant in 1970 traveled about 2900 kilometers (1800 miles), while in the year 2000 they traveled roughly 3650 kilometers (about 2300 miles). Since then, the trend has most likely continued its upward movement, as emerging economies now have a much larger potential market to find employment in.

For your average job-seeker, the low cost of travel opens up a host of new opportunities. An Indonesian migrant might previously have been limited to finding work in other Asian economies, like South Korea or Singapore. With the cost-effectiveness of a plane ticket now, compared to their projected income, means they can now buy a plane ticket and show up for a job on a cruise ship leaving from Miami. In fact, they may be able to make the intercontinental flight every few months in between jobs.

And while other transportation markets are exploring more cost-effective ways of fueling up, from electric cars to solar-powered ships, airplanes remain inflexibly dependent on oil. So, how sustainable is this – especially with two volatile markets—oil and airlines—in play? Could travel be more expensive ten years from now?

Fortunately, the “energy intensity” or “carbon footprint” of flying (the amount of energy consumed per passenger) has decreased by about 75% since 1970, according to Michael Sivak of the University of Michigan’s Transportation Research Institute. Planes have gotten much more energy-efficient: they are designed for better fuel economy, making it more sustainable for them to carry more passengers. In 1970 most flights were taking off half full, as regulations kept prices high and lack of analytical software limited airlines’ ability to fill planes. Today’s flights tend to be about 83% full, translating to lower costs for each passenger. These trends make it unlikely that we will see ticket prices return 1970s-levels, though they will certainly fluctuate, as they are now, with energy costs.

Emerging economies have a lot to gain from out-migration, especially given the easy access they have to the rest of the world. They are also benefiting from the reverse as cheap travel has made tourism a much bigger industry for industrialized and emerging economies worldwide. Tourists who had previously been limited by their budget to closer destinations can now travel wherever they like without major differences in cost.

The rise of the internet has even enabled “digital nomads” from America and Europe to live in countries like Morocco, Thailand, Columbia, and more, even as migrants from those countries send money home from abroad. Affordable energy continues to draw the world closer together, improving lives on both sides of the equation.