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