Photos: Lie-flat economy class pods are coming soon

The world's first lie-flat "pods" are coming soon to the economy class of an airplane.

Air New Zealand has announced that the pods will be launched in 2024. It had been working on its SkyNest concept for five years.

The seats are fully flat, made up with real mattresses plus cooling pillows and bedding, and located in the back of the plane, right behind the premium economy cabin.

However, the seats won't be included in the price of an economy ticket. SkyNests are a separate product, bunk beds stacked three high, and bookable only in four-hour increments, the amount of time the airline has determined it takes to allow guests two sleep cycles (which are typically about 90 minutes), with additional time to wind down and wake up.

Each aircraft being fitted with them will have six of these pods.

Air New Zealand already has a lie-flat option in economy, called the SkyCouch. It allows fliers to extend specially-designed footrests from all three seats in an economy row, to effectively widen those seats and turn the section into a makeshift bed. It's extremely popular with families, who can lay horizontally across a row they've booked together.

SkyNests will go into service on Air New Zealand's ultralong-haul nonstop routes, such as Chicago or New York to Auckland.

The carrier is also overhauling its cabin amenities as a whole, from business all the way back to economy, with lighter-weight designs that are meant to cut back on carbon emissions.