were flying
Las aves volaban haciendo formaciones.
The birds flew in formations.
Estudió cómo volaban las aves.
He studied how birds flew.
Los aviones volaban por encima del pueblo.
The planes were flying over the town.
Estudiaba cómo volaban la aves.
He was studying how birds flew.
Brillantes mariposas volaban de aquí para allá.
Bright butterflies flew to and fro.