(Reuters) - The Federal Aviation Administration is calling back 1,700 aviation safety inspectors as a partial government shutdown drags on into its fourth week.

Travelers wait in a security line at Reagan Washington National Airport in Arlington, Virginia, U.S., January 13, 2019. REUTERS/David Shepardson/File Photo

An FAA spokesman said on Tuesday it is “recalling inspectors and engineers to perform duties to ensure continuous operational safety of the entire national airspace. We proactively conduct risk assessment, and we have determined that after three weeks it is appropriate to recall inspectors and engineers.”

The FAA said it will have 2,200 aviation safety inspectors on the job by the end of this week, up from 500 last week. In total, the FAA will have 3,100 safety employees on the job as part of its safety efforts by the end of this week.

After the callbacks, 14,000 FAA of the 44,000 FAA employees will remain off the job. FAA employees, including more than 23,000 air traffic controllers, are working without pay.

FAA approval of aircraft such as Boeing’s MAX and new routes like Southwest Airlines Co’s Hawaii launch are on hold. The FAA said it is not immediately recalling employees who handle certifications of new aircraft.

Southwest confirmed on Monday its plans to launch service to Hawaii early this year were on hold because the FAA groups that oversee the route authorization process are on furlough. The airline said it will not announce any timelines for selling or operating flights to Hawaii until it receives the necessary authorization.

The partial government shutdown is also affecting the certification program for U.S. business jet maker Gulfstream Aerospace’s new G600 corporate plane, along with other “facets of our business,” a company spokeswoman said on Monday by email,

Savannah-based Gulfstream, a division of General Dynamics Corp had previously expected to obtain FAA certification or approval for the G600 by late 2018.

American Airlines Group Inc said it has taken delivery of two new MAX 8, but the planes are sitting idle in Tulsa, Oklahoma awaiting FAA approvals required for commercial operation.

The Transportation Security Administration said on Tuesday unanticipated absences of its 51,000 screeners rose to 6.8 percent Monday, up from 2.5 percent a year ago. TSA said security waits remained normal with the exception of Atlanta.

The U.S. Travel Association estimated on Tuesday that the estimated travel impact of the partial shutdown is $100 million daily for the U.S. economy, including the impact of suspended National Park services.