Both the Bona Fide Resident Test and the Physical Presence Test apply to American expats. The Bona Fide Resident Test applies to those expats who live overseas and have no plans of returning to the US. To pass the Physical Presence Test, though, one must simply be away from the US for more than 329 out of 365 days. It is important to keep this test and its qualifications in mind when traveling to and from the US. Passing this tax test will greatly reduce, maybe even eliminate, your US taxes.
Keep in mind that each day spent on US soil is counted against you. Even if you simply fly in for an afternoon meeting, the entire day will be deducted. There are significant tax credits and exclusions available to those who can prove physical presence in a foreign country (including the Foreign Housing Credit, the Foreign Earned Income Exclusion, and the Foreign Tax Credit). Therefore, whenever possible, it behooves expats to remain in the US for less than thirty-five of every 365 days.
The Physical Presence Test applies to any 365-day timeline. It can be counted from any day of any month. The test is very cut and dry and there are no exceptions counted for emergency travel. Any time spent on US soil counts against the necessary 330 days. Additionally, travel days (when traveling to the US) also count against the 330 days. Even if you pass the physical presence test and qualify for the exclusions, you might still be presented with a tax bill by the IRS. This is due to the fact that the exclusion only applies to money earned on foreign soil.
If your goal is to occupy two homes, one on US soil and one abroad, it will not be beneficial for you to try and claim expat exemptions. If, however, your intention is to primarily occupy your foreign residence and spend very little time on US soil, you should plan your time in the US very carefully. If you can easily lower your time in the US to less than 35 days, the effort will probably be well worth it (depending on your taxable income). Consult an international tax expert to be sure you will qualify for the exclusions and credits available to you.