(NewsNation) — Authorities in Texas arrested six undocumented migrants earlier this week attempting to charter a plane from Weslaco, Texas, in the Rio Grande Valley to Houston as part of a human smuggling operation.

The migrants, four men and two women from El Salvador and Mexico, were caught with fraudulent Texas identification cards at the Mid-Valley Airport and turned over to United States Border Patrol.

One of the men was later determined to be a deported felon who was wanted in Wisconsin for allegedly sexually assaulting a child.

Authorities arrested a 21-year-old woman, a U.S. citizen, who was coordinating the smuggling attempt to Houston. Two other men suspected of aiding in the attempt were also arrested and now face federal charges.

Officials with the Texas Department of Public Safety say it’s the third time in the last 30 days that state authorities have caught private planes attempting to smuggle undocumented migrants into the country.

Last week, authorities stopped a smuggling flight carrying 19 illegal migrants in McAllen, Texas.

In some cases, those migrants are paying thousands of dollars for a seat on the plane, Lt. Chris Olivarez, with Texas DPS, told NewsNation.

In August, one of the migrants caught on a smuggling flight told officials they paid $11,000 to get from the Dominican Republic to Houston.

The flights — which often land at small municipal airports — can be challenging to track and are becoming more common, Olivarez said.

The problem is further complicated by the fact that the pilots flying the charter planes can be unaware they are transporting illegal migrants, Olivarez noted. He pointed out that most are simply given a passenger list with names and they’re not required to verify anyone’s immigration status.

This week’s plane bust is just the latest evidence that human smuggling comes in many forms.

As the number of migrants attempting to enter the U.S. hits record highs, the methods for smuggling people into the country have become increasingly desperate and inhumane.

In June, 53 migrants died after being abandoned in a sweltering semitrailer in what authorities believe was part of a human smuggling operation.

For the first time ever, the total number of migrant encounters at the southern border has surpassed 2 million in a single fiscal year, according to U.S. Customs and Border Protection (CBP).