Despite Donald Trump’s promise to move forward with the “full repeal of Obamacare” on his first day in the Oval Office, Sen. Bill Cassidy, R-La., predicted Thursday that it would take about two years to repeal and replace the Affordable Care Act.

“If you build a better airplane, you want to make sure you have a better runway that can handle that plane,” Cassidy told Yahoo News and Finance Anchor Bianna Golodryga.

He insisted that a sufficient transition period would be needed between repealing portions of President Obama’s key legislation through reconciliation and replacing them with new legislation. The delay would help avoid anxiety for patients currently undergoing intensive treatments such as chemotherapy, he said.

Cassidy, a physician, has sponsored two alternatives to Obamacare since he entered the U.S. Senate in January 2015. The Patient Freedom Act, which Cassidy introduced last May, would allow states to opt out of Obamacare mandates for individuals and employers, instead offering incentives to those who choose to enroll.

Earlier this year, Cassidy joined forces with Republican Rep. Pete Sessions on what they called the “World’s Greatest Healthcare Plan Act of 2016.” Rather than repeal the Affordable Care Act, the Sessions-Cassidy plan would simply make Obamacare optional, providing those who opt out with tax credits that they could put toward a private insurance plan or a health savings account.

Cassidy pointed to both of his proposals when asked how he plans to protect the approximately 20 million people currently covered by Obamacare.

As for how long he expects this process to take, Cassidy told Golodryga, “We gave a two-year transition period for both the Obamacare to wind down and for the replacement to wind up. Two years sounds reasonable.”

Watch full interview below: