Since September 2005, anyone travelling by air will be required to present an identification document when checking in and boarding. Originally, this affected only those travelling on international flights. Since May 1, 2006, this also applies to those travelling on domestic flights.

The following identification documents are acceptable:
SIS identity card and service card
Driving licence
Passport and national identity card
Airlines must check passenger identities to ensure that the person who checked in for a flight is the same person who is on the aircraft. This identity control has been or will shortly be introduced by a number of other EU countries.
The Swedish Transport Agency (Transportstyrelsen) has introduced this requirement in stages:
Stage 1, international flights: Since September 2005, these requirements apply to Swedish as well as foreign airlines.
Stage 2, domestic flights: Since May 1, 2006, the same requirements also apply for domestic flights.
More information from the Swedish Transport Agency
National identity card replaces passport in the Schengen Area
A national identity card was introduced on October 1, 2005. This card contains information about Swedish citizenship and can therefore be used for travel in the Schengen Area as well as proof of citizenship. Travellers who do not hold a national identity card will be required to produce their passport for travel in the Schengen Area.
Acquiring a national identity card
Applications for the national identity card should be sent to a national police passport office. Photographs will be taken at the passport office to ensure quality and eliminate any risk of identification errors. The national identity card costs SEK 400 and is valid 5 years.
Reason for introducing identity cards
The EU requires all member states to guarantee that the person checking in baggage is also a passenger on the same flight. This is nothing new and has been a requirement in Sweden for the last ten years. Airlines must guarantee that the same number of people who checked in also take a seat on the same flight.
However, the EU Commission has a different interpretation. The Commission wants guarantees that the person checking in baggage is also the same person who is a passenger on the flight. This interpretation requires all EU member states to introduce identification controls.