A Boeing 727 operating as Iberia Flight 610 crashes Mount Oiz in Spain, killing 148; it is the deadliest accident to occur in Iberia's history and the deadliest in Basque County to occur.

The Boeing 727 is an American narrow-body airliner that was developed and produced by Boeing Commercial Airplanes. After the heavier 707 quad-jet was introduced in 1958, Boeing addressed the demand for shorter flight lengths from smaller airports. On December 5, 1960, the 727 was launched with 40 orders each from United Airlines and Eastern Air Lines. The first 727-100 rolled out on November 27, 1962, first flew on February 9, 1963, and entered service with Eastern on February 1, 1964.

Iberia Flight 610 was a scheduled domestic passenger flight from Madrid to Bilbao, Basque Country, Spain. On 19 February 1985, a Boeing 727-200 operating the flight crashed into a ravine after one of its wings sliced a television antenna on the summit of Mount Oiz in Biscay during an approach to Bilbao Airport. All 141 passengers and 7 crew on board died. The crash is the deadliest aviation disaster in both the Basque Country and Iberia history.

Mount Oiz, is one of the most popular summits of Biscay in the Basque Country (Spain). Its summits form part of a long range that feeds several rivers: Ibaizabal, Artibai, Lea, Oka and Deba in Gipuzkoa all of them running to the Bay of Biscay.

Iberia, legally incorporated as Iberia Líneas Aéreas de España, S.A. Operadora, Sociedad Unipersonal, is the flag carrier of Spain. Founded in 1927 and based in Madrid, it operates an international network of services from its main base of Madrid–Barajas Airport. Iberia, with Iberia Regional and with Iberia Express, is a part of International Airlines Group. In addition to transporting passengers and freight, Iberia Group carries out related activities, such as aircraft maintenance, handling in airports, IT systems and in-flight catering. Iberia Group airlines fly to over 109 destinations in 39 countries, and a further 90 destinations through code-sharing agreements with other airlines.