Oslo police have made four arrests following a hand grenade explosion in Pilestredet on Tuesday evening. The incident, which occurred at approximately 8:15 PM, involved one grenade that detonated and another that failed to explode but was safely handled by authorities. No injuries were reported, though police emphasized the significant damage potential of the explosion.

Two 13-year-old boys were initially taken into custody on Tuesday night, with two additional older teenagers arrested on Wednesday evening. The older suspects are both above the criminal age of responsibility and have been charged with involvement in serious illegal handling of explosives. Police confirm that the two 13-year-olds remain in the care of child protection services and will be interviewed again on Thursday.

Investigators are working under the hypothesis that the explosion is connected to conflicts between criminal actors. Police Inspector Grete Lien Metlid stated that the leading theory suggests the teenagers may have taken on a "violence as a service" assignment, carrying out the attack on behalf of others. The target appears to have been a business premises near the explosion site rather than specific individuals.

The investigation continues to examine potential connections to a separate kidnapping case involving a 24-year-old man last week. Police are exploring whether there might be a motivational link, given that the kidnapping victim reportedly has family ties to the business owner operating from the premises near the explosion site. Authorities have not commented on possible international criminal connections and emphasize that further arrests remain possible as the investigation progresses.

Finnair is gradually restoring its Airbus A321 fleet to service after an uncertified cleaning procedure forced the grounding of eight aircraft. The airline confirmed that seat covers were washed with water, a method not properly certified to ensure fire protection standards were maintained. This safety concern prompted the removal of the affected aircraft from service, leading to operational disruptions across Finnair's European network.

The situation began improving over the weekend as Finnair started installing new seat covers on the grounded aircraft. The first A321 returned to service on Sunday, operating a flight from Helsinki to Rhodes. However, seven aircraft remain out of service with no confirmed timeline for their full return. The A321s typically seat approximately 200 passengers and are crucial for Finnair's European route operations.

The grounding has resulted in significant passenger disruptions, with Finnair implementing extensive rebooking procedures. On Sunday alone, approximately 460 passengers were moved to different flights due to aircraft downgrades. The airline has prioritized high-frequency routes such as Helsinki-Stockholm and Helsinki-London, ensuring alternative options are available. In some cases, Finnair has used smaller replacement aircraft and offered incentives for volunteers to switch flights.

To manage the capacity shortfall, Finnair has wet-leased two aircraft with crews from Danish carrier DAT since Wednesday. While flight cancellations have decreased to single digits in recent days, with some days passing without any cancellations, the airline acknowledges that irregularities may continue through the coming week. Finnair is providing accommodation and compensation to affected passengers in accordance with EU air passenger rights regulations as it works to fully resolve the operational challenges.