CAIRO — The crash of a military transport plane that killed 257 people on Wednesday was Algeria’s deadliest ever, compounding the woeful air safety record of an insular country where there has been little accountability for such disasters in the past.

A Russian-built Ilyushin plane carrying soldiers and civilians slammed into a field moments after it took off from Boufarik military base, about 15 miles southwest of the capital, Algiers. The plane exploded into flames, sending black smoke billowing into the air. Only a handful of people survived.

The cause of the crash was not immediately known, and Algeria’s Defense Ministry began an investigation. But there was little prospect of any political repercussions in a country that has come to be seen as the region’s hermitlike giant, hesitant and inward-facing, as its economic and political malaise has deepened.

Rich in gas and oil, and the largest country in Africa by size, Algeria should loom large over the region. It avoided the turmoil of the Arab Spring uprisings that engulfed its North African neighbors Tunisia, Libya and Egypt. And it has established itself as a bulwark against Islamist extremism.