At the same time as earning a graduate engineering degree in the U.S. can be a grand way for international students to sharpen their English skills and gain cultural exposure, not everyone has the opportunity to quit their job or move their family abroad.

For students with limited mobility, online education can be a more realistic alternative. In the year 2013, international students made up about 7% of 12,870 students who pursued online engineering degrees at the master's programs ranked by U.S. News.

Admissions at the most highly ranked online graduate engineering programs can be economical, ranging anywhere from 44% to 90% at the top ten schools, the U.S. News data show. Like their U.S. peers, international students would need to have great grades, stellar references and strong test scores to get into those programs. In some cases, though school officials look at applications from international students through a different lens.

While it comes to international applications, admissions officials say English proficiency is their foremost concern. The capability to write well is important in all graduate programs, but particularly for online students, who require to spend even more time writing than their on-ground counterparts, they say.

Most online engineering schools require international students to have certain scores on exams for instance the Test of English as a Foreign Language or TOEFL, for admission. However that is not the only way students have to be prepared to demonstrate their English, says Dale Harris, executive director of engineering professional education at Purdue University Lafayette. The Indiana based school has No. 6 online graduate engineering program.

Engineering graduate programs that need the GRE tend to put most of their emphasis on quantitative scores, he says. But international students will be wise to also prioritize their verbal and writing scores, still if they do well on the language tests.

"In our case we don't have cut off scores or anything like that, however if we are dealing with a person whose admissibility is marginal, we may take a look at those things," says Harris. "They are perhaps a little more important."

At Connecticut's University of Bridgeport, where 70% of online engineering students are international, the GRE also plays a large role in the admissions process, says administrator Justin Hume.

"Since of the variance in international education, we put a little more focus on standardized tests scores," says Hume, assistant director of international admissions for all programs. "It is different but it levels the playing field for all kids."

In adding to having strong English writing skills, international students must also speak the language fluently, experts say. At Purdue, for instance, students are expected to participate in group projects, so knowledge of English is key, Harris says.

Wayne Pferdehirt, ‎director of graduate engineering distance degree programs at University of Wisconsin Madison, ranked No. 3, says his program puts such an emphasis on communication capability that students are necessary to interview by phone.

"With written materials, someone might hire someone to edit their materials," he says. "But in the verbal interview we get a better sense of which they are their aptitude to interact meaningfully with someone remotely."

In addition to English proficiency, international students have to also consider how their employment may affect their admissions chances. In some online graduate engineering programs, for example, international students who are by now working at a renowned company have a distinct advantage.

The engineering program at the University of Southern California's Viterbi School of Engineering, ranked No. 4, only accepts students who are affiliated with partner companies for example Chevron and Boeing, says Kelly Goulis, senior associate dean of graduate and professional programs.