Uhhhhhhh they probably don't have a good opinion of her skills, right, she can pretend to be shit at these controls and start "over correcting" - each time missing the beam by a hair.

A short time later, Pidge reports, "We're in." 

They delay a few seconds more, but then it's untenable to keep up the charade - 

They start to fight back.

The Galra were not expecting this! They recover quickly, though, and start fighting back. Swarms of tiny little red-and-black fighters come pouring out of the massive cruiser to engage the two Lions. 

Over the comms:

"Shiro! What's wrong?" 

       "I'm okay. I just...I've been here before. These corridors...I remember this ship. It's the one that captured us on the Kerberos mission."

"You don't have to come with me. You could wait in the Lion—"

       "I'll be fine, Keith. Let's move."

"Wait! Shiro, if this is the same ship, do you think—could the rest of your crew be here?" 

       "I—don't know. It's possible."

"We have to look for them! You've been here before, right? So you know the way to where they keep the prisoners. If there's even a chance—" 

"Keith, are you—"

       "I've got this, Shiro. Go." 

"Alright. Good luck." 

He doesn't really have time to tell them they're likely being dumb, given how busy he is fighting the Galra.

He's not as good a pilot as Nuray, but he's still going to give them a hell of a fight.

He'll keep this up until the others succeed, hopefully.

They manage to draw the fight out for a while, but as powerful as the Lions are, two of them against a whole fleet is a battle they're not going to win. 

Eventually, a small group of Galra ships manage to herd Akira into the path of the tractor beam. Before he has time to notice where they are, he's caught. 

The Blue Lion hangs limp and unresponsive as it's pulled inexorably towards the cruiser. 

And that's when a blast of energy hits the source of the beam, disrupting it just long enough for Akira to break free.

The Red Lion enters the fight at full speed, tearing through the little Galra fighters like they're made of paper and gouging lines of fire down the side of the cruiser with its claws. 

He's shaken, but only for a moment. 

He rejoins the fight.

With three Lions—four once Green weighs in as well—the tide turns. Working together, they're able to damage the forcefield protecting the cruiser's planet-destroying ion cannon, and then take the cannon itself out of commission.

With that accomplished, Allura calls them back. Now Sendak won't be able to destroy the planet as he threatened, they can safely retreat inside the castle's particle barrier, a bright blue sphere of interlocking hexagons similar to the ones the Lions generate. They need to unlock the fifth Lion before they can hope to defeat this fleet permanently. 

How do they do that?

Allura directs them to land their Lions in a hangar that's easily big enough for all of them, arrayed in a sort of semi-circle facing a massive pair of doors marked with the same V-shaped symbol that's on all the paladins' chest plates. 

Shiro, also under Allura's instructions, gets out of the Green Lion and stands in front of the big doors. He looks kind of shaken—something must have happened on the Galra ship.  

Once he's in position...

All of...

...the Lions' eyes...

...start...

...to glow. 

In response, the lines of the doors in front of them light up as well. With a majestic slowness, they part, sliding outwards to reveal a Lion that's as much larger compared to Yellow and Blue as they are to Red and Green. The Yellow Lion's head looks like it would come up to about the Black Lion's shoulder. 

On the Lion's back are a pair of folded red wings, made of the same alien metal as the rest.

Its eyes light up as they lock onto Shiro, and it throws back its head and roars. A moment later, the other four echo it, and the paladins can feel the Lions' elation at being together again for the first time in millennia. 

Eeee!

"Awesome!"

He's smiling.

"So what now?"

"Now, you form Voltron, and defeat Sendak once and for all!"

"...Uh. How?"

Frantic alarms begin blaring. The castle's sensors detect a massive shape descending through the atmosphere along with a host of smaller ones. Warning lights flash red in every Lion's cockpit.