I was reading an article in the online edition of El País about the collapse of airlines when the opening paragraph puzzled me
El 15 de diciembre de 2006 cerraba la línea aérea Air Madrid tras una larga serie de cancelaciones y retrasos. Dejó 7,5 millones de euros sin devolver en billetes emitidos hasta esa fecha y miles de pasajeros en tierra. Air Comet se quedó con sus rutas. Pero Air Comet cerró también de la noche a la mañana el 21 de diciembre de 2009 dejando tirados a otros miles de viajeros a ambos lados del Atlántico.
I understand what it means, this is not a request for translation, but the first verb cerraba is in what I would call in English the imperfect whereas the following ones are in the preterite (or simple past). In fact the article goes on with airlines which cerró, quebraron, dejó de operar, and so on.
Can anyone throw any light on this? Is it a mistake? Is it what is called in English elegant variation where you change just for variety (which many people frown on)?, Is it some feature of Spanish tenses which I have not yet learned?
The full article is here if that helps.