I could aviate you could aviate he could aviate we could aviate you could aviate they could aviate
V-ing form
I could be aviating you could be aviating he could be aviating we could be aviating you could be aviating they could be aviating
Perfect
I could have aviated you could have aviated he could have aviated we could have aviated you could have aviated they could have aviated
V-ing perfect
I could have been aviating you could have been aviating he could have been aviating we could have been aviating you could have been aviating they could have been aviating
Negation
Simple form
I couldn't aviate you couldn't aviate he couldn't aviate we couldn't aviate you couldn't aviate they couldn't aviate
V-ing form
I couldn't be aviating you couldn't be aviating he couldn't be aviating we couldn't be aviating you couldn't be aviating they couldn't be aviating
Perfect
I couldn't have aviated you couldn't have aviated he couldn't have aviated we couldn't have aviated you couldn't have aviated they couldn't have aviated
V-ing perfect
I couldn't have been aviating you couldn't have been aviating he couldn't have been aviating we couldn't have been aviating you couldn't have been aviating they couldn't have been aviating
Interrogative form
Simple form
could I aviate? could you aviate? could he aviate? could we aviate? could you aviate? could they aviate?
V-ing form
could I be aviating? could you be aviating? could he be aviating? could we be aviating? could you be aviating? could they be aviating?
Perfect
could I have aviated? could you have aviated? could he have aviated? could we have aviated? could you have aviated? could they have aviated?
V-ing perfect
could I have been aviating? could you have been aviating? could he have been aviating? could we have been aviating? could you have been aviating? could they have been aviating?
Interro-negative form
Simple form
couldn't I aviate? couldn't you aviate? couldn't he aviate? couldn't we aviate? couldn't you aviate? couldn't they aviate?
V-ing form
couldn't I be aviating? couldn't you be aviating? couldn't he be aviating? couldn't we be aviating? couldn't you be aviating? couldn't they be aviating?
Perfect
couldn't I have aviated? couldn't you have aviated? couldn't he have aviated? couldn't we have aviated? couldn't you have aviated? couldn't they have aviated?
V-ing perfect
couldn't I have been aviating? couldn't you have been aviating? couldn't he have been aviating? couldn't we have been aviating? couldn't you have been aviating? couldn't they have been aviating?