Poder + estar + infinitive vs poder + infinitive

Question

Good morning.What is the difference in meaning between "Poder + estar + infinitive" vs "poder + infinitive"?

Accepted Answer

Hola Ama
The difference between "poder + estar + present participle" and "poder + infinitive" is that the first and longer structure is using a progressive tense. Progressive tenses are formed by estar + present participle, e.g. estoy cantando, estábamos jugando..., therefore, when combined with a modal verb like poder, you are adding that progressive/continuity aspect to that verbal structure:

Ellos pueden estar jugando en esta sala. 
They can be playing in this room.
María podría estar subiendo a ese avión ahora.
María could be boarding that plane now.

However, with poder + infinitive, there is no progression/continuity:

Ellos pueden jugar en esta sala.
They can play in this room.
María podría subir a ese avión ahora.
María could board that plane now.

I hope this clarified it.
Saludos
Inma