revenue recognition over time
occurs when one of two conditions exist
-customer controls asset as it is created or enhanced
-company does not have an alternative use for asset created or enhanced and either
a)customer receives benefits as company performs the task, or
b) company has a right to paykent and this right is enforceable

one or both criteria are met in long-term construction contract accounting
-long-term contracts frequently provide that seller may bill purchaser at intervals
-examples
development of military and commercial aircraft
weapons delivery systems
space exploration hardware