Deep Vein Thrombosis (DVT): This is a common condition associated with long-distance travel, especially when seated for extended periods, such as on flights. The risk is increased due to immobilization, dehydration, and potential hypercoagulability. Bilateral feet swelling could be a manifestation of DVT, especially if it occurs in the context of recent travel.

Fluid Retention: Travel across time zones and changes in diet and physical activity can lead to fluid retention, which may cause swelling in the feet.
Cellulitis or Skin Infection: Travelers may be exposed to different pathogens, and skin infections can cause localized swelling. However, bilateral involvement might suggest a systemic cause or a common exposure.
Lymphedema: Though less common, lymphedema could be a consideration, especially if the patient has a history of surgery, infection, or trauma affecting the lymphatic system.

Pulmonary Embolism (PE): While PE itself does not directly cause bilateral feet swelling, it is closely related to DVT and can be life-threatening. Any suspicion of DVT warrants consideration of PE.
Nephrotic Syndrome: This condition, characterized by significant proteinuria, hypoalbuminemia, and edema, could present with bilateral swelling. It's crucial to consider systemic diseases that could lead to edema.
Heart Failure: Right-sided heart failure can cause peripheral edema, including swelling in the feet. This diagnosis is critical to consider due to its implications for patient management and prognosis.

Lipoedema: A chronic condition characterized by the abnormal distribution of fat cells, leading to swelling, typically in the legs. It's less likely but should be considered in the differential for bilateral leg swelling without an obvious cause.
Filariasis: Given travel to the Middle East, though less common in this region compared to other parts of the world, filariasis could cause lymphedema. It's a rare consideration but important in the context of international travel.
Sarcoidosis: This systemic disease can cause edema among its myriad presentations, though it would be an uncommon cause of bilateral feet swelling as an isolated symptom.