Airports operator AENA said all flights were halted at Barajas airport from 11:50 a.m. (1050 GMT), adding to the misery of passengers already suffering weeks of delays and cancellations due to industrial action by Iberia pilots.
Iberia operates 600 flights a day in and out of the four-runway airport, which handles more than 50 million passengers a year.
Madrid's regional government convened a meeting of its crisis committee and raised its warning level to orange -- the second highest -- as snow fell through the day and settled on the capital's streets for the first time since February 2005.
A transport department spokesman said all Madrid's major highways were jammed as a result of the bad weather.
The National Meteorology Institute said 10 cm (4 inches) was expected to fall in Madrid on Friday and further snow would fall over much of the country during the weekend.
The high north and central Spanish plateau sees deep snow every winter, but although Madrid sits at 650 metres above sea level, the city's heat makes snow a rarity.
Television pictures showed a lone cross-country skier in San Sebastian taking advantage of the wintery conditions across the country, using the northern town's main beach as a trail.
Last Mod: 09 Ocak 2009, 14:55