Aircraft Sentence Completion

The question asks us to choose the most appropriate phrase to complete the sentence: "The aircraft_______ take off as soon as its flight plan was filed." To correctly complete the sentence, we need to ensure that the chosen phrase fits grammatically and logically with the rest of the sentence, especially considering the verb tense.

Analyzing the Sentence Context

The key part of the sentence that guides our choice is the phrase "as soon as its flight plan was filed".

• The verb "was filed" is in the simple past tense. This indicates that the action of filing the flight plan happened at a specific point in the past and is now complete.
• Since the filing of the flight plan happened in the past, the subsequent action (the aircraft taking off) must also have happened or been permitted to happen in the past, immediately following the filing.
• Therefore, we need a phrase that expresses permission or allowance in the past tense.

Evaluating the Options for Tense and Meaning

Let's examine each option provided:

• 1. is allowed to

  • This phrase uses the present tense ("is allowed").
  • If we use this, the sentence would be: "The aircraft is allowed to take off as soon as its flight plan was filed."
  • This creates a mismatch in tenses. "Is allowed to" (present) does not logically follow "was filed" (past). The permission would have been granted in the past, not in the present, if it was directly related to a past event.

• 2. will be allowed to

  • This phrase uses the future tense ("will be allowed").
  • If we use this, the sentence would be: "The aircraft will be allowed to take off as soon as its flight plan was filed."
  • Again, this creates a tense mismatch. A future permission cannot be tied to a past event ("was filed") in this direct sequential manner. The permission to take off should have occurred at the same time or immediately after the past filing.

• 3. was allowed to

  • This phrase uses the simple past tense ("was allowed").
  • If we use this, the sentence would be: "The aircraft was allowed to take off as soon as its flight plan was filed."
  • This option perfectly aligns with the tense of "was filed." It indicates that the permission for the aircraft to take off was granted in the past, immediately after its flight plan was also filed in the past. This maintains consistent past tense throughout the description of sequential events.

• 4. has been allowed to

  • This phrase uses the present perfect tense ("has been allowed").
  • If we use this, the sentence would be: "The aircraft has been allowed to take off as soon as its flight plan was filed."
  • While the present perfect tense connects a past action to the present, in this specific context, the simple past "was allowed to" is more appropriate for describing a completed action that occurred at a specific point in the past, following another specific past action ("was filed"). The simple past provides a clearer sequence of events in the past. "Has been allowed to" would imply that the permission *still holds* or that the action's effect *is still relevant now*, which isn't the primary focus when stating a direct consequence of a past filing.

Conclusion on Correct Phrase

Based on the analysis of tense consistency and the sequence of events, "was allowed to" is the most appropriate phrase. It correctly places both the filing of the flight plan and the granting of permission for the aircraft to take off in the past.