Benign Paroxysmal Positional Vertigo (BPPV): This condition is a common cause of vertigo, especially after a change in environment or travel, which could involve air travel or other forms of transportation that might precipitate or exacerbate symptoms. The recent return from a study abroad trip could be a contributing factor due to the potential for changes in sleep patterns, stress, or even minor head injuries during travel.

Vestibular Migraine: Given the recent travel and potential changes in sleep patterns, stress levels, or exposure to new environments, vestibular migraine is a plausible diagnosis. It can cause vertigo and dizziness without the headache phase.
Labyrinthitis: An inner ear infection that could be contracted during travel, especially if the individual was exposed to others who were sick. It can cause vertigo, dizziness, and sometimes hearing loss.
Middle Ear Problems: Issues such as a middle ear infection or Eustachian tube dysfunction could lead to vertigo and dizziness, especially if the individual experienced barotrauma during flights.

Stroke or Transient Ischemic Attack (TIA): Although less common, vertigo can be a presenting symptom of a stroke or TIA, especially in the posterior circulation. It's crucial to rule out these conditions due to their high morbidity and mortality.
Multiple Sclerosis: While less likely, an initial presentation of multiple sclerosis could include vertigo and dizziness among other neurological symptoms.
Posterior Circulation Infarct: Similar to stroke, an infarct in the posterior circulation can present with vertigo and should be considered due to its potential severity.

Meniere's Disease: An inner ear disorder that involves vertigo, but it typically includes hearing loss and tinnitus, which might not be present in this case.
Acoustic Neuroma: A benign tumor on the nerve connecting the inner ear to the brain, which could cause vertigo among other symptoms like hearing loss.
Mal de Débarquement Syndrome: A rare condition that some people experience after a cruise or boat travel, characterized by a feeling of swaying or imbalance after returning to land.