I've heard that a number of people ____ forced to wait at the airport due to inclement weather conditions.arewaswereis

The correct word to fill in the blank in the sentence is "were."

Explanation:

1. Subject-Verb Agreement: The subject of the sentence is "a number of people," which is plural. Therefore, it requires a plural verb form.
2. Tense: The context of the sentence suggests that the waiting occurred in the past since it refers to a situation caused by "inclement weather conditions."

The complete sentence is: "A number of people were forced to wait at the airport due to inclement weather conditions."

Using "was" or "is" would be incorrect in this context as "was" suggests a singular subject or present perfect, neither of which applies here. Thus, "were" is the appropriate choice.