Alaska Airlines Boeing 737's inner windshield CRACKS while landing at Portland International Airport - following a litany of abysmal issues with the planes

The windshield on an Alaska Airlines flight from Washington D.C. cracked as it made its descent into Portland International Airport on Sunday night. 

The plane, a Boeing 737-800, was carrying 159 passengers and 6 crew members across the country when it suffered a small crack on the inner windshield.

'The crew followed their checklists and the aircraft continued safely to its destination as scheduled. Alaska Airlines' 737 fleet are outfitted with five-layer windscreens that have an outer pane, three inner layers and an inner pane. 

'If an inner pane cracks, the other pane and layers can maintain cabin pressure.' a statement from the airline read.

Alaska say the aircraft will be inspected and repaired by engineers on the ground.

An Alaska Airlines flight from Washington D.C. to Portland, Oregon suffered a cracked windshield, with 159 passengers and 6 crew onboard (file photo)

Despite the crack on the inner windshield, the crew of the Boeing 737 safely landed the aircraft (file photo)

The crack comes after a series of mishaps involving Boeing planes since the start of the year.  

In January, a door plug blew off an Alaska Airlines Boeing 737 Max 9 jetliner shortly after it took off from Portland International Airport. 

The blow out prompted several investigations and the grounding of similar planes.

On Monday, the CEO of United Airlines was moved to reassure passengers that the airline is safe after two recent incidents also involving Boeing aircraft. 

They include a wheel falling from an Osaka-bound jet in early March to a panel blowing off a plane shortly after it took off from San Francisco last week. 

'Safety is our highest priority and is at the center of everything we do,' Kirby said in an email to customers on Monday. 

'Unfortunately, in the past few weeks, our airline has experienced a number of incidents that are reminders of the importance of safety.' 

An Alaska Airlines Boeing 737-MAX 9 lost a door mid-flight in January, with several incident involving Boeing-made planes occurring since

Passengers had their phones and clothes ripped off by the force of the door blowout in January, with the incident sparking a lawsuit from the passengers 

United Airlines CEO Scott Kirby (pictured) sent an email to customers on Monday saying that 'safety is our highest priority and at the center of everything we do' 

Boeing's market value dropped by 11.57 percent over the past month, including a 4.49 percent dip over the last five days alone

Last Friday, a Boeing 737 jet was found to have a missing panel after it landed in Oregon. A tire also fell from a United Boeing 777 shortly after take off from LAX.

'Unfortunately, in the past few weeks, our airline has experienced a number of incidents that are reminders of the importance of safety,' Scott Kirby said. 'While they are all unrelated, I want you to know that these incidents have our attention and have sharpened our focus.' 

Kirby said United's teams are reviewing each case to understand what happened. 

The Federal Aviation Administration is also investigating the worrying incidents, which Kirby described as 'all unrelated' in an email to customers.

He also stressed how the company will use what it learns in safety training and procedures.

The aviation industry has come under the microscope after a string of recent mishaps unfolded, beginning with a door blowing off an Alaska Airlines Boeing 737 Max 9 on January 5. 

In the latest incident, a United Airlines plane from San Francisco built by Boeing was grounded Friday after it was found to be missing a panel after it touched down.

United went on to reveal that it was the wing-to-body fairing that ripped off - a part is located on the underside of the aircraft where the wing meets the aircraft body.

The panel sits just adjacent to where the landing gear deploys, and serves as a protective shell between the wing and the fuselage.

The plane is a Boeing 737-824, and successfully touched down in Medford Airport in Oregon despite the missing part. 

No injuries were reported and the Boeing aircraft was not a new model or a MAX.

The incident is the latest from the embattled manufacturer - and the seventh involving a Boeing plane in 10 days. 

Judd further clarified the part fell off midflight, as feds continue to look into Boeing's production practices.

A United Airlines plane built by Boeing was grounded on Friday after it was found to be missing a panel after it touched down following a flight. Pictured: The missing part on the Boeing 737

A few days earlier, on another United flight, a wheel fell off a Boeing 777-200 shortly after takeoff from San Francisco 

As was the case with the other mishaps, it occurred shortly after takeoff, and saw the 256lb wheel crush several cars parked below after falling to the ground 

Earlier this month a United Airlines aircraft skidded off a runway into a grassy area after a rough landing in Houston

The aircraft suffered some form of gear collapse as it exited the runway at George Bush Airport in Houston. The 160 passengers and six crew were not injured

Just three days before, a Boeing plane was forced to land due to hydraulic fluid spewing from its landing gear area. It was also a United Flight.

Also under investigation, the forced landing happened as the San Francisco-bound 777-300 embarked from Sydney, with fluid filmed leaking from its undercarriage.

It also comes less than a week after a former Boeing staffer was found dead by an apparent suicide, while doing depositions for a suit he filed against the firm alleging he witnessed second-rate parts being fitted on planes.

After the incident last Monday - and another hours before that saw 50 passengers injured on the firm's flagship 787-Dreamliner that took a sudden nosedive, believed to have been caused after a pilot's seat slammed into the control column.

The FAA has since revealed the firm failed 33 of 89 audits during an exam of Boeing's 737 Max - a model it had been planning to update with the long delayed Max 10.

In another incident, a Boeing plane was forced to land due to hydraulic fluid spewing from its landing gear area. The technical failure also occurred in midair on a United Airlines flight

Meanwhile, ex Boeing Quality Manager John Barnett - who had been in the midst of a whistleblower retaliation suit against the manufacturer - was found dead from what police said was a self-inflicted gunshot wound Saturday, while meeting Boeing lawyers in South Carolina

A file photo show Boeing employees walk the company's new, flagship 787-10 Dreamliner down towards the delivery ramp at the company's facility in South Carolina

After the incident - and the several before - United Airlines requested the firm halt work on the unreleased jets: an apparent sign of carriers' diminishing faith.

The Boeing whistleblower found dead, 62-year-old John Barnett, had given stark warnings over the aviation giant's 787 Dreamliner and 737 MAX models specifically in an interview, just weeks before his demise.

In the midst of a deposition in a whistleblower lawsuit in Charleston related to production of the 787 Dreamliner plane, Barnett was found with a 'self-inflicted' gunshot wound in the parking lot of a hotel in Charleston, South Carolina.

The Federal Aviation Administration is investigating nine incidents this month alone involving United planes.