Enter Air

When one Boeing 737 after another lifts off toward the Mediterranean from Warsaw, Katowice or Gdańsk on a summer morning, the odds are good that it belongs to Enter Air. The Polish charter airline is little known outside its home country – and that is exactly what makes it interesting for spotters. Behind the unassuming name are Poland’s largest private airline, an all-737 fleet and stakes that bring Enter Air aircraft as far as Zurich and Dublin.

Enter Air at a glance

Enter Air is a Polish charter airline based in Warsaw. It was founded on October 15, 2009, by a small group of experienced aviation people who had met earlier at Centralwings, the former low-cost offshoot of LOT Polish Airlines. The first flight went from Warsaw to Enfidha in Tunisia on April 25, 2010 – at the time still with two older Boeing 737-400s.

The airline has grown strongly since then. Enter Air has been listed on the Warsaw Stock Exchange since December 2015 and describes itself as the largest private Polish airline. For 2025 the group reported revenue of just under three billion zloty. By its own account, Enter Air flies to more than 30 countries and has already served almost 250 airports.

The business model differs clearly from scheduled and low-cost airlines such as Ryanair or Wizz Air. Enter Air flies mostly on behalf of tour operators: in Poland, customers include Rainbow Tours, TUI and Itaka, plus operators from other countries. Typical destinations are in Greece, Turkey, Spain, Portugal, Italy, Bulgaria, Croatia, Egypt and Tunisia.

Codes and callsign

• IATA code E4: appears in the flight number, so on the departure board and in travel documents.
• ICAO code ENT: appears in the air traffic control flight plan and on most flight trackers.
• Callsign ENTERAIR: how the crew identifies itself on the radio.

On charter flights it is especially worth checking the tracker, because the flight number on the departure board does not always tell you which aircraft is actually coming. If Enter Air leases other operators’ aircraft with crew in peak season, a flight with an E4 number can be operated by an entirely different carrier. How IATA and ICAO codes relate is explained in the article IATA and ICAO codes explained, and the difference between flight number and callsign in the guide Callsign vs. flight number.

The fleet: all Boeing 737

Enter Air has relied on the Boeing 737 from day one. The 737-400s started things off, and the last of them left in October 2017. Today the airline’s own fleet consists of two types. For summer 2026 the airline cited about 40 aircraft in service:

Type	Count (summer 2026)	Seats	Spotter note
Boeing 737-800	just over two dozen	189	Backbone of the fleet, many aircraft taken over second-hand
Boeing 737 MAX 8	12	189	Brand new from Boeing, registrations of the SP-EX… series
Wet-lease aircraft	2	varies	Other operators in their own livery

The Boeing 737-800 is the workhorse: it replaced the 737-400 and still makes up the majority of the fleet. The Boeing 737 MAX 8 joined Enter Air at the end of 2018. Shortly afterward it had to stay on the ground worldwide following the two crashes at other airlines; from March 2021 it flew again at Enter Air. Since then the MAX share has been growing step by step.

In 2026, two more MAX 8s came directly from Boeing: SP-EXL landed in Warsaw at the end of March after a nonstop ferry flight from Seattle, and SP-EXM followed in mid-May with a fuel stop in Stavanger. According to Enter Air, SP-EXM was the twelfth MAX and the 37th Boeing 737 in the airline’s history. Originally five new MAXs were planned for 2026; in August 2026 the airline’s management announced it would take at most one more MAX by the end of the year so as not to bring new aircraft into the weak winter. For 2027, Enter Air expects about ten percent more aircraft.

There is no Airbus in the airline’s own fleet. In some years between 2014 and 2023, however, leased Airbus A320s from other operators flew for Enter Air – such sightings are rare exceptions today.

737-800 or 737 MAX 8? How to tell them apart

At Enter Air, both types wear the same livery and have the same seat count. From the outside, a few details tell you which generation is rolling past.

The engines are the safest clue: you can see the serrated trailing edges of the MAX engines clearly on approach even with a medium focal length. If you are still unsure about the 737 generations, the article Identifying aircraft types for beginners helps.

The Enter Air Group: Chair and Fly4

Enter Air is more than a single airline. Counting the stakes, the group had about 49 aircraft in summer 2026. For spotters in Switzerland and western Europe, two companies are particularly interesting:

Airline	Based in	Enter Air stake	Codes	What you see
Enter Air	Poland	–	E4 / ENT	Boeing 737s with SP- registrations
Chair Airlines	Switzerland	just under half	CS / CSW	Airbus A319/A320 with HB- registrations, and Enter Air 737s when capacity is short
Fly4 Airlines	Ireland	51 percent, rest with TUI	F4 / FFA	Boeing 737-800s with EI- registrations on wet lease

In 2019, Enter Air acquired a stake in Switzerland’s Germania Flug AG, which shortly afterward became Chair Airlines. When Chair is short an aircraft, Enter Air can step in with one of its own Boeing 737s. Then a Polish 737 stands at the gate in Zurich even though the flight runs under a Chair flight number. If you spot at Zurich Airport, for example from Observation Deck B or the Butzenbüel, it is best to watch for such guests.

Fly4 Airlines was created in 2023 as a joint venture with the TUI Group and is based at Dublin Airport. The Irish aviation authority issued the air operator’s certificate in March 2024, and Fly4 performed its first commercial flight a few days later out of Liège on behalf of TUI. The airline flies four Boeing 737-800s where sisters such as TUI fly Belgium or TUIfly need capacity at peak times. The principle behind it is explained in Wet leasing explained.

How to recognize Enter Air

The easiest way to place Enter Air is the combination of a Boeing 737, a Polish registration and the ICAO code ENT. In Poland, Enter Air shares the apron with LOT, which also uses 737 MAX 8s on medium-haul routes, and with Buzz of the Ryanair Group, which also carries SP- registrations. The livery separates the three at first glance; when sorting your photos, the registration helps as well. How registrations are structured is explained in Understanding aircraft registrations and in the overview of country codes on aircraft.

The schedule also reveals a lot. Charter flights often depart very early in the morning or late at night so that an aircraft can complete several rotations to the holiday destinations per day. If you want to see Enter Air, you therefore often need an early alarm – or you plan specifically for the return waves in the afternoon and evening.

Spotting Enter Air: when and where

Your best chances are in Poland. Warsaw Chopin and Katowice are the main bases, plus Poznań, Gdańsk and Wrocław. The new SP-EXM also landed at Warsaw Chopin Airport after its ferry flight. In peak season, several Enter Air 737s often stand side by side there in the morning before the first wave departs toward the south.

In winter the picture changes. Part of the fleet keeps flying to warm destinations, but many aircraft go into maintenance. For the 2026/27 season, Enter Air plans to carry out at least 60 percent of maintenance itself – in two hangar bays in Katowice and one in Debrecen, Hungary. So if you look for Enter Air in winter, you are more likely to find it in Katowice than on the holiday routes.

Outside Poland you meet Enter Air mainly at the holiday airports around the Mediterranean – at the destination, not the departure airport. Add to that the operations for Chair in Zurich and flights for foreign tour operators, which Enter Air serves in addition to its Polish customers.

Before you set out, it is worth looking at the runway direction in use. How to read it from wind and schedule is explained in Understanding the runway direction in use. New to the hobby? Then start with Plane spotting for beginners.

Common mix-ups

• Equating an E4 flight number with an Enter Air aircraft – in peak season, leased aircraft from other operators also fly under E4.
• Assuming every Polish 737 belongs to Enter Air – LOT and Buzz also fly Boeing 737s with SP- registrations.
• Classifying Enter Air as a low-cost carrier – it flies mostly for tour operators, not through classic individual seat sales.
• Dismissing an Enter Air 737 in Zurich as a misidentification – under a Chair flight number it is a legitimate operation.
• Thinking Fly4 is a TUI airline – Fly4 is majority-owned by Enter Air, with TUI holding the minority.
• Recognizing the 737 MAX 8 only by the winglets – the serrated engine cowlings are the more reliable feature.

Conclusion

Enter Air is the quiet giant of Polish holiday traffic: an all-Boeing 737 fleet, almost exclusively charter for tour operators and a small group with stakes in Switzerland and Ireland. If you note down the registration and ICAO code, you recognize not only Enter Air itself but also the wet-lease guests under E4 flight numbers and the Polish 737s working for Chair.