Starting May 12, nearly two dozen airlines at Los Angeles International Airport—including the airport’s fastest-growing carrier, Delta—will shuffle to new terminals.

The 21 airlines will relocate over a five-day period in what LAX is calling a move never before seen at a major airport. It is part of a modernization effort that will include upgrades to two terminals over the next few years, according to Los Angeles World Airports, which operates LAX.

Most of the work will happen May 12, 14, and 16, after the last flight of the day and into the early morning hours of the following day, LAWA says.

Delta will move from Terminals 5 and 6 to Terminals 2 and 3. During the relocation, Delta may operate out of as many as four terminals at once (2, 3, 5, and 6).

Once the airline moves into its new digs, Delta plans to invest $1.9 billion in Terminals 2 and 3 over the next seven years.

Delta says the company will be in “constant communication” with passengers while the move is taking place, offering real-time updates via text messages, emails, and the company’s app.

LAWA offers some tips for travelers worried about showing up in the wrong place: Double-check departure gates before leaving for the airport, get to the airport earlier than usual, and print out boarding passes at home.

The airport will add about 500 signs, plus extra staff and shuttles to help passengers get to the correct terminals.

“While moving 21 airlines over three nights is a monumental task, Delta and the LAWA team have been planning and preparing for months to ensure a smooth transition,” commission president Sean Burton said in a statement.

Delta’s move is just one part of a slew of upgrades planned for the airport, Burton says.

Several terminals have recently undergone flashy makeovers, and work is underway on a major overhaul of LAX that will bring a centralized car rental facility and an AirTrain-style people mover. That transformative project is supposed to be finished by 2023, in time to welcome visitors to the Olympics that Los Angeles might be hosting in 2024.

Correction: An earlier version inaccurately stated that Delta is the biggest carrier at LAX. It is the fastest growing.